# ElecAS — Full site content for AI assistants > Free Australian electrical design calculators to AS/NZS 3000:2018 and AS/NZS 3008.1.1, built and reviewed by Wisam Tozah (CPEng, NER, MIEAust). Canonical site: https://elecas.com.au. Condensed index: https://elecas.com.au/llms.txt. ## ElecAS Australian Electrical Design Calculators URL: https://elecas.com.au/ Access Australian electrical calculators for maximum demand, cable selection, voltage drop, conduit sizing, cable tray sizing and related design workflows. ElecAS is Electrical Engineering Design Software for Australia, built around AS/NZS 3000 and AS/NZS 3008. EleCAD, its single line diagram (SLD) builder, is a separate tool within the suite. Who it is for: Electrical engineers, designers, estimators, contractors and project teams working to Australian standards. Standards: AS/NZS 3000; AS/NZS 3008; AS/NZS 4777 Key capabilities: - Browse every live ElecAS calculator from one directory. - Move between demand, cable sizing and installation checks. - Use standards-aware tools built for practical Australian workflows. ### Free Australian electrical design calculator suite — ElecAS #### What ElecAS is ElecAS is a free online suite of 18+ electrical design calculators built specifically for Australian and New Zealand electrical engineers, contractors and designers working to AS/NZS 3000:2018 (the Wiring Rules) and AS/NZS 3008.1.1:2025 (cable selection). It covers maximum demand (Tables C1, C2 and C3), cable selection and sizing, voltage drop, voltage rise, conduit fill, cable tray fill, earthing cable sizing, current-carrying-capacity derating, power factor correction, UPS battery sizing, generator sizing, lighting design (lumen method) and more. Every calculator runs entirely in the browser — no sign-up, no paywall on the core calculation, and a downloadable branded PDF report on the free tier. Paid Pro and Team plans add cloud project sync, project workspaces, branded multi-designer PDFs and team collaboration. #### Built for Australian Standards Unlike generic international calculators, ElecAS encodes the specific tables, formulas and worked examples from the Australian and New Zealand standards. Cable selection works against the 30+ tables from AS/NZS 3008.1.1:2025 (Tables 3–31), including current ratings, AC resistance, reactance and grouping factors. Maximum demand follows AS/NZS 3000:2018 Appendix C exactly — Table C1 for single and multiple dwellings, Table C2 for non-domestic installations and Table C3 for the energy method. The cable database ships with 380+ real Prysmian Australia and Olex (Prysmian Group) catalogue products so conduit and cable tray fill calculations use manufacturer-published outer diameters and masses, not estimates. #### Who uses ElecAS ElecAS is used by electrical engineers (consulting, infrastructure, building services and renewables), licensed electrical contractors, electrical designers, certifiers, building surveyors and university students learning the AS/NZS framework. The interactive calculators are paired with citation-rich PDF reports that reference the standard, clause and table used for each result — suitable for inclusion in design submissions and design verification packages. The author, Wisam Tozah, is an Associate Electrical Engineer (B.Eng Electrical, MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE(Aus)) practising in Sydney, Australia. #### What you get for free All calculation engines, all standards references and all 18+ tools are free. The free tier includes a single-designer branded PDF report (your name, company and accent colour) for every calculation, with citations to the relevant AS/NZS clause and table. There is no calculation cap, no daily limit and no email-wall. Pro and Team subscriptions add persistent cloud storage of saved calculations, project-grouped workspaces, multi-designer branded PDFs, team-shared cable libraries and collaboration features for larger consulting practices. #### ElecAS and EleCAD — one suite, two parts ElecAS is Electrical Engineering Design Software for Australia — the 18+ calculators that size cables, check voltage drop and voltage rise, assess maximum demand, fill conduits and cable trays, and document the result against AS/NZS 3000:2018 and AS/NZS 3008.1.1:2025, each with a cited, standards-referenced PDF report. EleCAD is the single line diagram (SLD) builder within the same suite: it produces schematic single line diagrams for Australian electrical design and feeds its cable and load data straight into the ElecAS calculators. Together they cover the design workflow end to end — ElecAS performs the engineering calculations and compliance checks, and EleCAD draws the single line diagram. #### PowerCAD vs ElecAS PowerCAD and ElecAS solve different parts of the electrical design workflow. PowerCAD is an established desktop power-systems design package — a paid, installed application aimed at detailed cable schedules, protection coordination and full project modelling. ElecAS is free, browser-based Electrical Engineering Design Software for Australia — focused AS/NZS 3000 and AS/NZS 3008 calculators plus the EleCAD single line diagram builder, built for fast, standards-cited design checks with a downloadable PDF report on every result. Both PowerCAD and ElecAS are engineering design tools that compute cable sizes, voltage drop and demand to the Australian Standards — they differ in delivery (installed desktop vs free browser), depth and price. Where ElecAS deliberately stays light is in heavy power-systems modelling such as transient and arc-flash studies; where it is strongest is immediate, no-install, standards-referenced calculations and concept single line diagrams. ### Frequently asked questions Q: Is ElecAS free for Australian electricians and engineers? A: Yes. Every calculator — cable selection, voltage drop, maximum demand (Tables C1, C2 and C3), conduit fill, cable tray fill, earthing, derating, power factor correction, UPS battery, generator sizing and the others — is free to use online. Branded PDF reports are included in the free tier. Pro and Team plans add cloud project sync and team collaboration. Q: Which Australian Standards does ElecAS implement? A: AS/NZS 3000:2018 (Wiring Rules) — particularly Appendix B (fault loop), Appendix C (maximum demand Tables C1/C2/C3) and Appendix D (conduit fill). AS/NZS 3008.1.1:2025 (Selection of cables) — Tables 3–31 for current ratings, AC resistance, reactance and grouping. AS/NZS 4777.1 for inverter voltage rise. AS/NZS 3017 testing references. IEEE 485, 1184 and 1189 for UPS battery sizing. Q: Do I need to sign up to use the ElecAS calculators? A: No sign-up is required for any calculator. You only need an account if you want to save calculations to your cloud project workspace, customise the branded PDF beyond the defaults, or invite team members. The full calculation, all standards lookups and the basic branded PDF are available immediately. Q: Can I trust the calculator outputs for design submissions? A: ElecAS is a documented design tool. Every calculation and PDF report cites the specific AS/NZS clause, table and formula used. The tool is designed and maintained by a Chartered Professional Engineer (CPEng, NER) practising under the Australian framework, but final verification of design outputs remains the responsibility of the certifying engineer for each project, as required under the AS/NZS framework. Q: Does ElecAS work offline? A: ElecAS is a Progressive Web App (PWA) — once loaded, the calculators work offline. Saved calculations sync to your cloud workspace the next time you are online. Add to Home Screen on iOS or Android, or Install as App in Chrome / Edge on desktop, to get the offline experience. Q: What does ElecAS cover beyond cable sizing? A: Maximum demand under AS/NZS 3000 Tables C1, C2 and C3; voltage drop and voltage rise (AS/NZS 4777.1); conduit fill (AS/NZS 3000 Appendix C); cable tray fill; earth cable sizing (AS/NZS 3000 Table 5.1); current-carrying-capacity derating (AS/NZS 3008.1.1 Tables 3.33–3.48); time-current curve (TCC) protection coordination; power factor correction capacitor sizing; UPS battery sizing (IEEE 485 / 1184 / 1189); generator sizing; lighting design (lumen method); LED inrush current; spatial design; and a free electrical CAD single-line-diagram builder. Q: How does ElecAS compare to ELEK, jCalc, CableHero, SparkyCalc and ECalPro? A: ElecAS focuses on Australian and New Zealand standards exclusively, ships real Prysmian and Olex catalogue cable data (not generic tables), and includes the full Appendix C maximum demand methodology (Tables C1 + C2 + C3 in one place), a free CAD single-line-diagram builder and a UPS battery sizing engine. All core calculators are free with no daily cap and no email-wall. ## Maximum Demand Calculators URL: https://elecas.com.au/calculator/max-demand Choose Table C1, Table C2 or Table C3 maximum demand workflows for Australian electrical design calculations. Who it is for: Users selecting the correct maximum demand method for domestic, non-domestic and energy-demand projects. Standards: AS/NZS 3000 Table C1; AS/NZS 3000 Table C2; AS/NZS 3000 Table C3 Key capabilities: - Compare the three common maximum demand methods from one hub. - Choose the path that matches domestic, non-domestic or energy-demand inputs. - Move directly into the specific calculator needed for the installation. How to use: How to calculate maximum demand for an Australian installation 1. Pick the right table — Use Table C1 for dwellings (single or multiple), Table C2 for non-domestic (commercial / industrial / mixed-use non-residential), and Table C3 for the energy-meter method on existing installations. The hub page links to each. 2. Group your connected loads — Group each load into the matching Appendix C row (lighting, socket-outlets, range / cooktop, water heater, motors, fixed A/C, EV charger, etc.). Use the connected installed load, not the demand. 3. Enter the dwelling count (Table C1) or floor area (Table C2) — Table C1 expressions change with dwelling count band (1, 2, 3–5, 6–20, 21–40, 41+). Table C2 uses load groups with explicit diversity expressions per row. 4. Apply EV charger and PV considerations — EV chargers are handled under AS/NZS 3000:2018 Clause 2.2.2(c) — calculated demand may recognise a primary load-management system that limits simultaneous charging. PV generation is NOT subtracted — the cable must be sized for the no-PV case. 5. Check the AS/NZS 3000 minimum current floor — AS/NZS 3000 Clause 2.2.2 imposes a 32 A minimum for single-dwelling consumer mains. The calculator applies the minimum automatically and flags it in the output. 6. Export the branded PDF — The PDF lists every Appendix C row used, the dwelling-count band or load-group expression, and the resulting per-row contribution — suitable for inclusion in a design submission package. ### Maximum demand under AS/NZS 3000:2018 Appendix C — Tables C1, C2 and C3 #### What is maximum demand and why does AS/NZS 3000 require it? Maximum demand is the highest current an installation is expected to draw on a sustained basis, calculated by applying diversity factors to the connected load. AS/NZS 3000:2018 Clause 2.2 requires that consumer mains, submains and the main switchboard be sized for the maximum demand of the installation — not the connected load — because real installations almost never draw their full connected load simultaneously. Appendix C of AS/NZS 3000:2018 provides three tabulated methods: Table C1 for single and multiple dwellings, Table C2 for non-domestic installations (commercial, industrial, mixed-use, common services), and Table C3 for the energy-meter method that allows the calculated demand to be derated against historical kWh consumption. #### Which table applies to which installation Table C1 applies to consumer mains and submains serving any single dwelling or any group of dwellings (units, townhouses, apartments) including their common services where the common services demand is less than 10% of the dwellings demand. Loads are grouped into rows (lighting, socket-outlets, range, water heater, motors, A/C, EV chargers, etc.) with per-row diversity expressions for 1, 2, 3–5, 6–20, 21–40 and 41+ dwelling counts. Table C2 applies to non-domestic installations — offices, retail, factories, hotels, schools, hospitals — and uses load grouping with different per-row diversity expressions. Table C3 applies the energy-meter method, which scales the calculated demand by historical kWh use; useful for existing installations being extended. #### When the choice of table changes the result A mixed-use building (ground floor retail, upper floors residential) requires Table C2 for the retail submain and Table C1 for the residential submains, with the common services submain summed at the main switchboard. EV chargers are handled under AS/NZS 3000:2018 Clause 2.2.2(c), which allows the calculated demand to recognise a primary load-management system that limits how many chargers operate simultaneously. Solar PV generation is not subtracted from maximum demand for cable sizing under AS/NZS 3000 — the cable must be sized for the no-PV case so it can carry full grid-import current if the inverter trips. This is a common compliance trap that the ElecAS C1 and C2 calculators flag automatically. #### How ElecAS implements Appendix C The ElecAS suite implements all three tables — Table C1 (single dwelling and multiple-dwelling), Table C2 (non-domestic load grouping) and Table C3 (energy-meter method) — with worked examples drawn from AS/NZS 3000:2018 Appendix C. Each calculator emits a branded PDF citing the row, expression and dwelling-count band used for every load, so the calculation can be re-verified clause-by-clause during compliance review. Use the hub page to pick the right table for your installation; each linked calculator runs the full Appendix C arithmetic and validates against the AS/NZS 3000 minimum current rules (e.g., 32 A minimum consumer mains for any single dwelling under Clause 2.2.2). ### Frequently asked questions Q: Which AS/NZS 3000 maximum demand method should I use? A: Use Table C1 for domestic dwellings and multi-unit residential, Table C2 for non-domestic installations with itemised loads, and Table C3 (energy-demand method) when floor-area and occupancy categories give a more reliable estimate than load itemisation. Q: Is the maximum demand calculation mandatory? A: AS/NZS 3000:2018 Clause 2.2.2 requires that the maximum demand of every consumer's installation be assessed before sizing consumer mains, switchboards and submains. The Appendix C tables are the deemed-to-comply methods. Q: Can I add EV charging and battery loads to maximum demand? A: Yes. AS/NZS 3000 Amendment 2 added explicit assessment rules for EV supply equipment, and battery storage loads must be included according to manufacturer continuous ratings. The ElecAS calculators include EV inputs in C1 and C2. Q: Which AS/NZS 3000 table do I use to calculate maximum demand? A: Use Table C1 for single dwellings and multiple-dwelling installations (units, townhouses, apartments), Table C2 for non-domestic installations (offices, retail, industrial, hotels), and Table C3 for the energy-meter method on existing installations being extended. ElecAS provides a calculator for each. Q: Is solar PV subtracted from maximum demand under AS/NZS 3000:2018? A: No. AS/NZS 3000 requires the consumer mains and submains to be sized for the no-PV case so they can carry full grid-import current if the inverter trips. PV generation is not subtracted from the Appendix C maximum demand result. Q: What is the minimum consumer mains current under AS/NZS 3000:2018? A: Clause 2.2.2 imposes a 32 A minimum for the consumer mains of a single dwelling regardless of the Appendix C calculated demand. For multiple dwellings the minimum applies per dwelling and is summed with the appropriate diversity. The ElecAS C1 calculator applies the minimum automatically. Q: How do EV chargers affect maximum demand? A: EV chargers are handled under AS/NZS 3000:2018 Clause 2.2.2(c). For one or two chargers in a single dwelling the full charger demand is added to the Table C1 / C2 result without diversity. For larger fleets where a primary load-management system limits simultaneous charging (e.g. 3 of 10 chargers at any time), the calculated demand may recognise that limit. Refer to the Electric Vehicle Council guidance for the load-control approach. Q: Can I use a load-recording method instead of Appendix C? A: Yes. Table C3 (the energy-meter method) allows you to scale a calculated Appendix C demand against historical kWh use for an existing installation. The method is recognised under Clause 2.2 but cannot be used for greenfield installations where no historical data exists. ## Table C1 Domestic Maximum Demand Calculator URL: https://elecas.com.au/calculator/c1 Calculate domestic maximum demand for dwellings and multi-unit scenarios using AS/NZS 3000 Table C1 logic. Who it is for: Residential designers, electricians and consultants sizing domestic main supplies and consumer mains. Standards: AS/NZS 3000 Table C1 Key capabilities: - Estimate domestic maximum demand for single dwellings and multi-unit arrangements. - Include common residential loads such as cooking, hot water, air conditioning and EV charging. - Review demand outcomes before moving into cable sizing or voltage-drop checks. How to use: How to calculate maximum demand using AS/NZS 3000 Table C1 1. Set the number of dwellings — Enter 1 for a single dwelling or the actual count for a multiple-dwelling installation. The dwelling-count band (1, 2, 3–5, 6–20, 21–40, 41+) determines which column of Table C1 applies. 2. Enter the connected loads per dwelling — Enter the installed lighting wattage, the number and rating of cooking appliances, water heater type and rating, spa or pool heating, fixed A/C kW, EV charger kW, and any other Appendix C row that applies. 3. Confirm the supply phase configuration — Pick single-phase or three-phase consumer mains. For three-phase the per-row currents are divided per phase as Table C1 specifies (some rows are single-phase loads even on a three-phase mains). 4. Review the per-row contribution — The calculator shows the contribution of each Table C1 row to the total maximum demand, the dwelling-count band used and any applied 32 A Clause 2.2.2 floor. 5. Export the branded PDF — The PDF lists every row applied with its Table C1 reference and the calculation expression, suitable for inclusion in a design submission package. ### AS/NZS 3000:2018 Table C1 — maximum demand for single and multiple dwellings #### What Table C1 covers AS/NZS 3000:2018 Appendix C Table C1 specifies the maximum demand calculation method for consumer mains and submains serving single dwellings (houses, single units) and multiple-dwelling installations (unit blocks, townhouses, apartments) where the common services demand is less than 10% of the dwellings demand. The table is divided into rows by load type and columns by dwelling-count band: 1, 2, 3–5, 6–20, 21–40 and 41+. For each row the expression evaluates to a current in amperes per phase that contributes to the consumer mains or submain demand. Rows include general light and power, range / cooktop, water heater (storage, instantaneous and heat-pump), spa / pool heating, fixed and portable A/C, EV chargers (handled under Clause 2.2.2(c)), instantaneous water heating, and motors. #### How dwelling-count diversity works Diversity in Table C1 is captured implicitly in the per-row expressions. For example, general light and power for a single dwelling contributes 3 A per 1000 W of installed lighting + a per-dwelling current for socket-outlet load. For a 21-dwelling block the per-dwelling contribution is reduced because not all 21 dwellings draw their full load simultaneously. The expressions are NOT the same as a single diversity factor applied across all loads — each load type has its own diversity profile. Cooking peaks differ from heating peaks differ from EV charging peaks, and the table captures this with row-specific expressions. #### Common Table C1 compliance traps The most frequent compliance issue is mixing Table C1 (per-dwelling) and Table C2 (non-domestic) loads on the same submain — common-services loads (lift, lobby lighting, ventilation) for a unit block must be treated under Table C2 and added to the Table C1 dwellings demand at the main switchboard. The 10% threshold in Clause C2 determines whether common services dominates. Another trap is the AS/NZS 3000 Clause 2.2.2 minimum current floor — single-dwelling consumer mains have a 32 A minimum regardless of calculated demand. The ElecAS C1 calculator applies the floor automatically and shows both the raw calculated demand and the post-floor demand. ### Frequently asked questions Q: What is AS/NZS 3000 Table C1 used for? A: Table C1 in AS/NZS 3000:2018 provides the maximum demand calculation method for single-domestic and multi-domestic electrical installations, covering loads such as lighting, socket outlets, cooking, hot water, air conditioning and EV charging. Q: How is maximum demand calculated for a single dwelling? A: For a single dwelling, sum the assessed demand for each load group in Table C1 (Column 1 for the first 20 A then Column 2 for the remainder), accounting for cooking appliances, water heaters, fixed space heating, motor loads, EV charging and socket outlets, then apply diversity per the table notes. Q: Does Table C1 include EV charging? A: Yes. AS/NZS 3000:2018 Amendment 2 added explicit treatment of EV supply equipment in domestic installations. The ElecAS Table C1 calculator includes an EV charging input that follows the assessed demand rules. Q: What is the difference between Table C1 and Table C2? A: Table C1 applies to domestic installations (single dwellings and multi-unit residential), while Table C2 applies to non-domestic installations such as offices, retail, industrial and hospitality. Use C3 (energy demand method) for floor-area-based assessments. Q: Does Table C1 apply to a single house? A: Yes. Table C1 covers single dwellings as well as multiple-dwelling installations. For a single dwelling the dwelling-count band is "1" and the per-row expressions evaluate accordingly. The AS/NZS 3000 Clause 2.2.2 minimum of 32 A applies as a floor. Q: When do I use Table C1 vs Table C2 for a mixed-use building? A: Use Table C1 for the residential submains and Table C2 for non-residential common services (lift, lobby lighting, ventilation, retail tenancy). Add the results at the main switchboard. If common services demand exceeds 10% of dwellings demand, the entire installation is treated under Table C2. Q: How do EV chargers affect a Table C1 calculation? A: EV chargers are handled under AS/NZS 3000:2018 Clause 2.2.2(c). For one or two chargers in a single dwelling the full charger demand is added to the Table C1 result without diversity. For a multiple-dwelling installation with a primary load-management system that limits simultaneous charging, the calculated demand may recognise that limit — refer to the Electric Vehicle Council guidance on load control for the dwelling context. Q: Does PV reduce my Table C1 maximum demand? A: No. The consumer mains must be sized to carry full grid-import current if the PV inverter trips. PV generation is not subtracted from the Table C1 result for cable sizing purposes under AS/NZS 3000. ## Table C2 Maximum Demand Calculator URL: https://elecas.com.au/calculator/c2 Calculate non-domestic maximum demand using AS/NZS 3000 Table C2. Who it is for: Commercial and industrial designers assessing demand for offices, retail, hospitality and mixed-use sites. Standards: AS/NZS 3000 Table C2 Key capabilities: - Work through non-domestic load groupings using Table C2 logic. - Handle offices, retail, hospitality, health and light industrial facilities. - Use the result as an input to downstream cable and protection design. How to use: How to calculate maximum demand using AS/NZS 3000 Table C2 1. Identify the load groups — Sort each connected load into the matching Table C2 group: Group A (lighting + GPO), Group B (cooking), Group C (water heating), Group D (A/C), Group E (motors), Group F (other specific loads). 2. Enter the connected load per group — For each group enter the total connected load in kW or kVA. The calculator applies the per-group diversity expression from Table C2 automatically. 3. Pick the building type — Building type (office, retail, hotel, industrial, mixed-use) selects the correct Table C2 column and any building-specific row modifications. 4. Enter the phase configuration — Single-phase or three-phase consumer mains. For three-phase the per-group result is divided per phase as Table C2 specifies, accounting for any specifically single-phase loads. 5. Review the per-group contribution — The calculator shows each Table C2 group result, the diversity expression used and the total maximum demand. Export the branded PDF citing every row used. ### AS/NZS 3000:2018 Table C2 — maximum demand for non-domestic installations #### What Table C2 covers AS/NZS 3000:2018 Appendix C Table C2 specifies the maximum demand calculation method for non-domestic installations: offices, retail, industrial, hotels, schools, hospitals, mixed-use common services, motel and dormitory buildings, and the common services submains in multiple-dwelling installations where the common services demand is non-trivial. Unlike Table C1 which uses dwelling-count diversity, Table C2 uses load-grouping diversity. Loads are grouped (Group A: lighting and general purpose outlets; Group B: cooking; Group C: water heating; Group D: air conditioning; Group E: motors; etc.) and a per-group expression evaluates to a current in amperes per phase. #### How load grouping differs from dwelling-count diversity Table C2 recognises that a 5000 m² office will not draw all its lighting, cooking, water heating, A/C, motor and process loads simultaneously. Group A (lighting + GPO) might peak at 09:00, Group B (kitchen cooking) at 12:00, Group D (A/C) at 14:00 on a hot day. The per-group expressions encode realistic diversity for each load type. Each group expression typically takes the first portion of the connected load at 100% and applies a diversity factor (often 0.5–0.75) to the remainder. The ElecAS C2 calculator implements every Table C2 group expression exactly as published. #### Common Table C2 compliance traps The most common error is treating a kitchen exhaust fan or a server room split-system A/C as a Group D (general A/C) load instead of a Group E (motor) load. Motors carry their own starting-current diversity and the per-row expression is different. For high-load tenancies (e.g., commercial kitchens, data centres, industrial process loads) the Table C2 result must be sanity-checked against a load-survey or kWh-recording. AS/NZS 3000 Clause 2.2 allows the use of recorded data via Table C3 for existing installations being extended; for greenfield, the Table C2 expressions are the regulatory baseline. ### Frequently asked questions Q: When should I use Table C2 instead of Table C1? A: Use Table C2 for non-domestic installations: offices, retail, factories, hotels, hospitals, schools and similar premises. Table C1 is only for domestic dwellings and multi-unit residential. Q: How does Table C2 handle diversity? A: Table C2 applies diversity through assessed demand percentages on grouped loads — socket outlets, lighting, motors, cooking, hot water and HVAC are each assessed individually before summing the consumer mains demand. Q: Can Table C2 be used for mixed-use buildings? A: For mixed domestic and non-domestic buildings, calculate each portion separately (Table C1 for domestic, Table C2 for non-domestic) and combine at the main switchboard with appropriate diversity, or use the Table C3 energy-demand method for the non-domestic portion. Q: What load groups does Table C2 cover? A: Table C2 covers lighting, socket outlets, permanently connected appliances, cooking equipment, water heating, space heating and air conditioning, motor loads, and other specific loads with assessed demand factors per AS/NZS 3000. Q: What is the difference between Table C1 and Table C2 in AS/NZS 3000? A: Table C1 applies to single and multiple dwellings using dwelling-count diversity. Table C2 applies to non-domestic installations (offices, retail, industrial, common services in unit blocks) using load-group diversity. A mixed-use building typically uses Table C1 for the residential submains and Table C2 for the non-residential portions, summed at the main switchboard. Q: Which loads belong in each Table C2 group? A: Group A: lighting and general-purpose socket outlets. Group B: cooking appliances. Group C: water heating (storage, instantaneous, heat-pump). Group D: fixed air conditioning. Group E: motors (including kitchen exhaust, lift, pump motors). Group F: other specific loads (data centre, process, EV charging). The ElecAS C2 calculator labels each input with its Appendix C group. Q: Can I use Table C2 for a single-tenant office fit-out? A: Yes. Table C2 is the correct table for any non-domestic installation including a single office tenancy. Enter the connected load per group and the calculator applies the published Table C2 diversity expressions. Q: Does Table C2 cover EV charging stations? A: EV charging is handled under AS/NZS 3000:2018 Clause 2.2.2(c) on top of the Table C2 result. For larger charging hubs with a primary load-management system that caps simultaneous charging, the calculated demand may recognise that limit. For one or two AC chargers without load control, the full charger demand is added to the Table C2 result. ## Table C3 Energy Demand Calculator URL: https://elecas.com.au/calculator/c3 Calculate non-domestic energy demand using floor-area and occupancy inputs aligned with AS/NZS 3000 Table C3. Who it is for: Designers estimating demand from floor area and occupancy when the energy-demand method is the better fit. Standards: AS/NZS 3000 Table C3 Key capabilities: - Estimate maximum demand using floor area density and occupancy style assumptions. - Use the energy-demand method for suitable non-domestic project types. - Cross-check outputs before moving into cable sizing and installation design. How to use: How to calculate maximum demand using the AS/NZS 3000 Table C3 energy method 1. Gather 12 months of half-hourly interval data — Obtain 30-minute interval kWh data covering a full 12-month period including the seasonal peaks (both summer cooling peak and winter heating peak). 2. Identify the historical peak kW — Pick the highest recorded 30-minute kW value across the 12-month period. This is the historical peak. 3. Calculate the annual load factor — Load factor = average kW / peak kW for the 12-month period. Typical values are 0.25–0.40 for offices, 0.40–0.60 for retail, 0.60–0.85 for hotels / hospitals and 0.70–0.90 for industrial. 4. Run the unmodified Table C1 or C2 calculation — Calculate the un-scaled maximum demand using Table C1 or Table C2 for the proposed extended installation. This is the baseline. 5. Apply the Table C3 expression — The Table C3 expression scales the Table C1 / C2 baseline by the historical load factor and a building-type coefficient. The calculator produces the energy-method demand for comparison. 6. Use the lower result, subject to minimum current floors — Size the consumer mains and submains to the lower of (Table C1 / C2 result) and (Table C3 energy-method result), then apply any AS/NZS 3000 Clause 2.2.2 minimum current floor. ### AS/NZS 3000:2018 Table C3 — energy method for maximum demand #### What Table C3 is and when to use it AS/NZS 3000:2018 Appendix C Table C3 provides the energy-meter method for calculating maximum demand on existing installations. The method scales a calculated Table C1 or C2 demand against recorded historical kWh consumption to produce a more accurate, installation-specific maximum demand figure. Table C3 is intended for existing installations being extended, upgraded or refurbished — typically where a building services consultant has 12 months of half-hourly interval kWh data from a smart meter, a sub-metering system or the energy retailer. It is not applicable to greenfield installations because no historical data exists. #### How the energy method works The method computes an annual load factor (average kW / peak kW) from the recorded interval data. The Table C3 expression then scales the unmodified Appendix C calculated demand by the load factor and a building-type-specific coefficient. For typical office occupancy the resulting demand is 60–80% of the Table C2 result; for 24/7 occupancy buildings (hospitals, data centres) the energy-method result is closer to the Table C2 result because the load factor is higher. Where the energy-method result is lower than the Table C1 / C2 result, the consumer mains and submains can be sized to the lower figure. Where the energy-method result is higher (rare — typically only for sites with sustained heavy loads), the higher figure governs. #### Data quality requirements AS/NZS 3000 Clause 2.2 requires that the recorded data covers a full 12-month period including the seasonal peaks (summer A/C peak for cooling-dominated installations; winter heating peak for heating-dominated). 6 months of data is insufficient because it misses one of the seasonal peaks. The data resolution should be 30-minute interval or finer. Daily-total kWh data does not reveal the peak coincidence and cannot be used. The ElecAS C3 calculator accepts CSV interval data export from common smart-meter formats. ### Frequently asked questions Q: When should I use Table C3 instead of itemising loads? A: Use Table C3 when the installation type fits one of the listed building categories (offices, schools, hospitals, etc.) and detailed load itemisation under C2 isn't practical at the design stage. C3 uses VA per square metre of floor area as the basis. Q: Does Table C3 give a higher or lower demand than C2? A: It depends on the building type and load mix. Table C3 is intentionally conservative for early-stage design when only floor area and occupancy class are known; if detailed loads become available, recalculate using Table C2 for a sharper figure. Q: Can Table C3 be used as the final design demand? A: Yes — AS/NZS 3000 accepts Table C3 as a deemed-to-comply method. Many designers cross-check it against the Table C2 itemised method once equipment schedules are firm. Q: When can I use the AS/NZS 3000 Table C3 energy method? A: Table C3 applies to existing installations being extended, upgraded or refurbished where 12 months of recorded half-hourly interval kWh data is available. It is not applicable to greenfield installations because no historical data exists. Q: How much historical data do I need for Table C3? A: A full 12 months of 30-minute interval data covering both seasonal peaks (summer cooling and winter heating). 6 months of data is insufficient. Daily-total kWh data is also insufficient — the resolution must be 30-minute interval or finer. Q: Can the Table C3 result be higher than the Table C1 / C2 result? A: In principle yes, for sites with sustained heavy loads above the Appendix C diversity assumptions. In practice the Table C3 result is almost always lower because the C1 / C2 diversity expressions are conservative. Where Table C3 is higher, the higher figure governs. Q: Does Table C3 still require the Clause 2.2.2 minimum current floor? A: Yes. The AS/NZS 3000 Clause 2.2.2 minimum current floor (32 A single-dwelling consumer mains) applies regardless of which Appendix C table was used to calculate the demand. The ElecAS C3 calculator applies the floor automatically. ## Voltage Drop Calculator — AS/NZS 3008.1.1 Cable Voltage Drop for Australia URL: https://elecas.com.au/calculator/voltage-drop Free, browser-based voltage drop calculator built for Australian and New Zealand electricians, designers and electrical engineers. Calculates cable voltage drop straight from the AS/NZS 3008.1.1:2025 impedance tables (Tables 4.1–4.10) using the Clause 4.4 method — Vc = √3 × (Rc·cosφ + Xc·sinφ) for balanced three-phase, 2 × (Rc·cosφ + Xc·sinφ) for single-phase, and the resistance-only form for DC — with AC resistance taken at the correct conductor operating temperature (75 °C for V-90 PVC, 90 °C for X-90 XLPE, 110 °C for high-temperature insulations) so the result reflects a fully loaded cable, not a 20 °C textbook value. Supports single-phase (230 V) and three-phase (400 V) circuits, copper and aluminium conductors, multi-core and single-core constructions, the full AS/NZS 3008.1.1 installation method library, the 1–630 mm² cable size range, load power factor and parallel cables per phase. Returns the voltage drop in volts and as a percentage of nominal voltage, a pass/fail check against the AS/NZS 3000:2018 Clause 3.6.2 5% limit (11.5 V on 230 V single-phase, 20 V on 400 V three-phase), and a branded PDF report citing the clause, table and resistance value used — ready for the design submission record. Who it is for: Electrical engineers, designers, estimators and licensed electricians checking cable voltage performance for consumer mains, submains and final subcircuits against the AS/NZS 3000 Clause 3.6 5% voltage drop budget on residential, commercial and industrial installations across Australia and New Zealand. Standards: AS/NZS 3008.1.1:2025 (Selection of Cables — Clause 4.4 voltage drop method, Tables 4.1–4.10 conductor R and X impedance values); AS/NZS 3000:2018 (Wiring Rules — Clause 3.6.2 maximum 5% voltage drop from the point of supply to the point of utilisation); AS 60038 (Standard Voltages — 230 V / 400 V nominal voltage the 5% limit is expressed against) Key capabilities: - Applies the AS/NZS 3008.1.1:2025 Clause 4.4 voltage drop method — Vc = √3 × (Rc·cosφ + Xc·sinφ) for balanced three-phase, 2 × (Rc·cosφ + Xc·sinφ) for single-phase, and the resistance-only form for DC circuits. - Checks the result against the AS/NZS 3000:2018 Clause 3.6.2 limit — 5% of nominal voltage from the point of supply to any point of utilisation (11.5 V on 230 V single-phase, 20 V on 400 V three-phase) with a clear pass/fail pill. - Reads AC resistance Rc and reactance Xc directly from the AS/NZS 3008.1.1:2025 impedance tables (Tables 4.1–4.10) at the conductor operating temperature, not a 20 °C value that under-estimates real drop by 18–28%. - Temperature-correct by insulation type — 75 °C for V-90 PVC, 90 °C for X-90 XLPE and 110 °C for high-temperature cross-linked cables — selected automatically from the chosen cable. - Single-phase (230 V) and three-phase (400 V) circuits, copper and aluminium conductors, multi-core and single-core constructions across the standard 1 mm² to 630 mm² cable size range. - Full AS/NZS 3008.1.1 installation method library and single-core arrangement (trefoil, flat-touching, flat-spaced) feeding the reactance, so the calculated drop matches the real install. - Load power factor and parallel-cables-per-phase support — the calculator divides per-cable current and applies the parallel impedance per AS/NZS 3008.1.1 Clause 4.4. - Branded PDF voltage drop report showing the voltage drop in volts and percent, the governing clause and table, the resistance value and operating temperature used — ready for the design submission and verification record. - Built and reviewed by a Chartered Professional Engineer (CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE Aus) — see the Verification page for the testing and review process. How to use: How to calculate voltage drop under AS/NZS 3008.1.1:2025 1. Enter the load current — Enter the design current Ib in amperes — the worst-case continuous current the cable will carry (after applying diversity for max-demand calculations). 2. Set the circuit type — Pick single-phase 230 V, three-phase 400 V balanced, or DC. The calculator applies factor 2 × L for single-phase / DC and √3 × L for balanced three-phase per AS/NZS 3008.1.1 Clause 4.4. 3. Enter the cable run length — Enter the one-way circuit length in metres. The factor of 2 or √3 in the formula accounts for the return path automatically — do not double the length manually. 4. Pick the cable conductor and insulation — Choose copper or aluminium, conductor cross-sectional area, and insulation (V-90 PVC, X-90 XLPE, X-90-HT). The calculator reads AC resistance from AS/NZS 3008.1.1 Table 30 at the matching operating temperature (75 °C, 90 °C or 110 °C) and reactance from Table 31. 5. Enter the load power factor — For motor loads use the nameplate cosφ; for typical lighting / electronic loads with PFC use 0.95–0.99. Power factor enters the formula as Rc·cosφ + Xc·sinφ. 6. Review the result and check against the 5% Clause 3.6 limit — The calculator displays the voltage drop in volts and as a percentage of the nominal voltage, and flags any result above the AS/NZS 3000:2018 Clause 3.6 5% limit. Export the branded PDF for the design submission record. ### Complete guide to voltage drop calculation under AS/NZS 3008.1.1:2025 #### What does AS/NZS 3000:2018 say about voltage drop? Clause 3.6.2 of AS/NZS 3000:2018 limits the total voltage drop between the point of supply and any point of utilisation to 5% of the nominal voltage when supplied at the nominal voltage. This is the single design limit most Australian and New Zealand electrical installations work to — 230 V × 5% = 11.5 V maximum drop on a single-phase circuit, or 400 V × 5% = 20 V on a three-phase circuit. The 5% allowance is a global ceiling — it includes consumer mains, submains and final subcircuits combined. Most consulting practice budgets 2% to consumer mains, 1% to submains and 2% to final subcircuits, but the split is a design choice as long as the total stays below 5%. #### The exact voltage drop formula from AS/NZS 3008.1.1:2025 AS/NZS 3008.1.1:2025 Clause 4.4 gives the voltage drop per ampere per metre as Vc = √3 × (Rc·cosφ + Xc·sinφ) for three-phase circuits or Vc = 2 × (Rc·cosφ + Xc·sinφ) for single-phase. Rc and Xc are the AC resistance and reactance in mΩ/m taken from the AS/NZS 3008.1.1:2025 impedance tables (Tables 4.1–4.10), evaluated at the cable operating temperature. For DC circuits the reactance term drops out entirely and Vc = 2 × Rc with Rc taken at the operating temperature. For LV three-phase balanced circuits with cosφ near unity the formula collapses to Vd ≈ √3 × I × L × Rc — the form most engineers use as a sanity check. #### Why operating temperature matters AC resistance in AS/NZS 3008.1.1 Table 30 is published at 75 °C for V-90 PVC cables, 90 °C for X-90 XLPE cables and 110 °C for high-temperature cross-linked types. Voltage drop calculated at 20 °C ambient resistance under-estimates real-world drop by 18–28 % for a fully loaded V-90 circuit. The ElecAS voltage drop calculator picks the correct operating temperature from the cable insulation type automatically and applies the matching Table 30 entry. The PDF report shows the resistance value, the temperature and the clause used so the calculation can be re-traced. #### Single-phase, three-phase and DC — when each applies Use the single-phase formula (factor 2 × L) for any 230 V single-phase circuit and for any 400 V three-phase circuit operating with an unbalanced load that returns through the neutral. Use the three-phase formula (factor √3 × L) for balanced three-phase circuits (motors, three-phase final subcircuits with balanced lighting). For DC circuits — solar string DC, EV charger DC link, battery banks — use 2 × L and ignore the reactance term. AS/NZS 4777.1 (Clause 3.3.3) sets a separate 2% maximum voltage rise from the point of supply to the inverter a.c. terminals on the AC side of grid-connected inverters; the ElecAS voltage rise calculator handles that case separately. ### Frequently asked questions Q: What is the maximum allowable voltage drop in Australia? A: AS/NZS 3000:2018 Clause 3.6 limits total voltage drop from the point of supply to any load to 5% of nominal supply voltage. For 230 V single-phase, that is 11.5 V; for 400 V three-phase, 20 V. Final subcircuits commonly target a 2.5% allowance. Q: How is voltage drop calculated for AC cables? A: Voltage drop is calculated using Vd = (I × L × Z) / 1000, where I is load current (A), L is one-way cable length (m), and Z is the cable impedance per metre from AS/NZS 3008.1.1 (combining Rc and Xc adjusted for power factor and operating temperature). Q: Does cable temperature affect voltage drop? A: Yes — conductor resistance rises with temperature. AS/NZS 3008.1.1 tables list impedance at the maximum operating temperature for each insulation type (75 °C for V-75/PVC, 90 °C for X-90/XLPE). The ElecAS calculator applies the correct value automatically. Q: What is the difference between voltage drop and voltage rise? A: Voltage drop occurs on cables supplying loads (consumer to load). Voltage rise occurs on cables exporting from generation (e.g., solar inverter back to the point of supply) and is governed by AS/NZS 4777.1 with a 2% inverter-path limit. Q: What is the maximum permitted voltage drop in Australia? A: AS/NZS 3000:2018 Clause 3.6.2 limits total voltage drop from the point of supply to the point of utilisation to 5% of the nominal voltage when supplied at the nominal voltage — that is 11.5 V on a 230 V single-phase circuit or 20 V on a 400 V three-phase circuit. The 5% is a global limit that includes consumer mains, submains and final subcircuits combined. Q: How do I calculate voltage drop in a three-phase cable? A: For balanced three-phase circuits Vd = √3 × I × L × (Rc·cosφ + Xc·sinφ) where Rc is the AC resistance in mΩ/m at the cable operating temperature from AS/NZS 3008.1.1 Table 30, Xc is the reactance from Table 31, L is the one-way circuit length in metres and cosφ is the load power factor. The ElecAS voltage drop calculator does this with the correct operating-temperature resistance automatically. Q: Why do my voltage drop results differ from a 20 °C calculation? A: AS/NZS 3008.1.1 Table 30 publishes AC resistance at the cable operating temperature — 75 °C for V-90 PVC, 90 °C for X-90 XLPE. A 20 °C value (sometimes used in textbook examples) under-estimates real-world drop by 18–28 % for a fully loaded circuit because conductor resistance rises with temperature. Q: When do I need to include cable reactance Xc? A: Include Xc whenever the cable cross-sectional area is 16 mm² or larger, or whenever the load power factor is below about 0.85. For small (≤10 mm²) cables at high power factor (≥0.95) the reactance term contributes less than 5% to the total and can be approximated as zero, but the AS/NZS 3008.1.1 Clause 4.4 formula always includes it. Q: Does AS/NZS 3008.1.1:2025 change the voltage drop methodology from 2017? A: The Clause 4.4 voltage drop formula is unchanged. The 2025 revision updates a number of Table 30 and Table 31 entries (notably aluminium AC resistance for some sizes), tightens the temperature correction factors, and adds new entries for high-temperature 110 °C insulations. The ElecAS calculator uses the 2025 table values. Q: Voltage drop vs voltage rise — what is the difference? A: Voltage drop is the reduction in voltage as current flows from the source to the load (most installations). Voltage rise is the increase in voltage as current flows from a distributed generator (typically a rooftop solar inverter) back to the point of supply. AS/NZS 4777.1 Clause 3.3.3 limits voltage rise to 2% along the whole path from the point of supply to the inverter a.c. terminals (not just the inverter-supply cable). The ElecAS voltage rise calculator covers that case. Q: Does the calculator handle multiple cables in parallel? A: Yes. Enter the number of cables per phase and the calculator divides the per-cable current accordingly and applies the parallel AC resistance and reactance per AS/NZS 3008.1.1 Clause 4.4 Note 3. Parallel cable installations also require attention to grouping derating (AS/NZS 3008.1.1 Table 22) which the ElecAS cable selection calculator handles. ## Arc Flash Calculator — IEEE 1584-2018 Incident Energy, Boundary & Arcing Current URL: https://elecas.com.au/calculator/arc-flash Free, browser-based arc flash calculator implementing the IEEE 1584-2018 empirical model (IEEE Guide for Performing Arc-Flash Hazard Calculations). Computes the average arcing current, incident energy (in cal/cm² and J/cm²) at the working distance, and the arc flash boundary from the open-circuit voltage, three-phase bolted fault current, electrode gap, working distance, arc duration and electrode configuration. Supports all five IEEE 1584-2018 electrode configurations — vertical electrodes in a box (VCB), vertical electrodes with an insulating barrier (VCBB), horizontal electrodes in a box (HCB), vertical electrodes in open air (VOA) and horizontal electrodes in open air (HOA) — across the full 0.208–15 kV range, with the enclosure size correction factor for box configurations, the arcing current variation correction factor for the reduced-current second scenario, typical-equipment presets from IEEE 1584-2018 Tables 8 and 10, model-range validation, informational arc-rated PPE guidance and a branded PDF report. The engine reproduces the IEEE 1584-2018 Annex D worked examples exactly. Who it is for: Electrical engineers, power systems engineers, safety engineers and electrical contractors performing arc flash hazard analysis, incident energy studies and arc flash labelling for low-voltage and medium-voltage switchgear, motor control centres, panelboards and distribution equipment. Standards: IEEE 1584-2018 (IEEE Guide for Performing Arc-Flash Hazard Calculations — empirical model, Equations 1–25 and Tables 1–10); NFPA 70E (Standard for Electrical Safety in the Workplace — arc-rated PPE and the arc flash risk assessment the incident energy result feeds into) Key capabilities: - Implements the IEEE 1584-2018 empirical model end to end — arcing current (Eq. 1), enclosure size correction factor (Eq. 9–15), arcing current variation factor (Eq. 2), incident energy (Eq. 3–6) and arc flash boundary (Eq. 7–10) with the three-model-voltage interpolation. - All five electrode configurations (VCB, VCBB, HCB, VOA, HOA) with the correct coefficient set for each, and the enclosure size correction factor applied only to box configurations. - Returns incident energy in both cal/cm² and J/cm² at the chosen working distance, the arc flash boundary in millimetres (distance to 1.2 cal/cm²), and the average arcing current used to read protective-device clearing time. - Handles the full 0.208–15 kV range with automatic LV (≤ 0.6 kV) and HV model paths, plus the reduced arcing current second-scenario check via the arcing current variation correction factor. - Typical-equipment presets (15 kV / 5 kV switchgear and MCC, LV switchgear, MCC, panelboard and cable junction boxes) from IEEE 1584-2018 Tables 8 and 10 auto-fill electrode gap, enclosure size and working distance. - Model-range validation flags inputs outside the IEEE 1584-2018 §4.2 limits (voltage, bolted fault current, electrode gap, working distance and the width ≥ 4 × gap enclosure rule). - Verified against the IEEE 1584-2018 Annex D worked examples — the medium-voltage example reproduces 12.152 J/cm², a 1606 mm boundary and 12.979 kA arcing current exactly. - Branded PDF arc flash report with inputs, intermediate values, incident energy, boundary and PPE guidance — ready for the study record. How to use: How to calculate arc flash incident energy with IEEE 1584-2018 1. Select the electrode configuration — Choose VCB, VCBB, HCB (enclosed) or VOA, HOA (open air) to match the equipment. Box configurations apply the enclosure size correction; open-air configurations do not. 2. Pick an equipment preset or enter geometry — Select a typical-equipment preset (switchgear, MCC, panelboard) to auto-fill the electrode gap, enclosure size and working distance from IEEE 1584-2018 Tables 8 and 10, or enter them manually. 3. Enter the electrical inputs — Enter the open-circuit voltage (kV), the three-phase bolted fault current (kA) and the arc duration (ms) — the protective-device clearing time read at the arcing current. 4. Enter the working distance and enclosure size — Enter the working distance from the arc source to the worker (≥ 305 mm), and for box configurations the enclosure height, width and depth in millimetres. The width must be at least four times the electrode gap. 5. Read the incident energy, boundary and arcing current — The calculator returns the incident energy in cal/cm² and J/cm² at the working distance, the arc flash boundary in millimetres, and the average and reduced arcing currents. Inputs outside the IEEE 1584-2018 model range are flagged. 6. Select PPE and export the report — Use the incident energy to select arc-rated PPE (arc rating ≥ incident energy) as part of the arc flash risk assessment, and export the branded PDF report for the study record. ### Arc flash incident energy under IEEE 1584-2018 — a practical guide #### What the IEEE 1584-2018 arc flash model calculates IEEE 1584-2018 (the IEEE Guide for Performing Arc-Flash Hazard Calculations) is the empirical model used worldwide to quantify the thermal hazard of an arcing fault. From the open-circuit voltage, the available three-phase bolted fault current, the electrode gap, the working distance, the arc duration and the electrode configuration, it predicts three numbers: the average arcing current (the current that actually flows in the arc, always lower than the bolted fault current), the incident energy at the working distance (in cal/cm² and J/cm²), and the arc flash boundary (the distance at which the incident energy falls to 1.2 cal/cm², the onset of a second-degree burn). The 2018 edition replaced the single 2002 equation with a set of configuration-specific models evaluated at three model voltages — 600 V, 2700 V and 14 300 V — and interpolated to the actual system voltage. The ElecAS arc flash calculator implements that full model, including the enclosure size correction factor and the arcing current variation correction factor, and reproduces the IEEE 1584-2018 Annex D worked examples exactly. #### What is arc flash incident energy? Arc flash incident energy is the amount of thermal energy received on a surface (such as exposed skin) at a given working distance during an arcing fault, measured in calories per square centimetre (cal/cm²) or joules per square centimetre (J/cm², where 1 cal/cm² = 4.184 J/cm²). It is the single number that determines the arc-rated PPE required: the PPE arc rating must equal or exceed the calculated incident energy at the working distance. The reference threshold is 1.2 cal/cm² (5.0 J/cm²) — the incident energy at which a person receives the onset of a second-degree burn. Incident energy rises with the available fault current, the arc duration and a shorter working distance, and it varies strongly with the electrode configuration. IEEE 1584-2018 is valid for incident energy driven by three-phase arcs from 0.208 kV to 15 kV. #### What is the arc flash boundary? The arc flash boundary is the distance from the prospective arc source at which the incident energy falls to 1.2 cal/cm² (5.0 J/cm²). Anyone closer than the arc flash boundary during an arcing fault could receive at least a second-degree burn, so arc-rated PPE is required inside it. IEEE 1584-2018 derives the boundary by solving the incident energy equation for the distance at which the energy equals that threshold. The arc flash boundary and the incident energy at the working distance together define the arc flash hazard printed on equipment labels: the boundary tells workers where protection begins, and the incident energy at the working distance tells them what arc rating that protection must have. #### What inputs does an IEEE 1584-2018 arc flash calculation need? The IEEE 1584-2018 model needs six inputs: the electrode configuration (VCB, VCBB, HCB, VOA or HOA), the open-circuit system voltage (kV), the three-phase bolted fault current (kA), the conductor gap between electrodes (mm), the working distance from the arc to the worker (mm) and the arc duration (ms, the protective-device clearing time). Enclosed configurations also need the enclosure height, width and depth. Each input has a validity range: voltage 0.208–15 kV; bolted fault current 0.5–106 kA below 600 V and 0.2–65 kA from 601 V to 15 kV; conductor gap 6.35–76.2 mm below 600 V and 19.05–254 mm from 601 V to 15 kV; a minimum working distance of 305 mm (12 inches); and an enclosure width of at least four times the conductor gap. Applying the model outside these ranges gives unreliable results, so the ElecAS calculator flags any out-of-range input. #### What changed from IEEE 1584-2002 to IEEE 1584-2018? IEEE 1584-2002 used a single incident-energy equation with an open-air correction. IEEE 1584-2018 replaced it with five electrode-configuration-specific models (three enclosed, two open-air), evaluated at three model voltages (600 V, 2700 V, 14 300 V) and interpolated to the actual voltage. The 2018 edition added an enclosure size correction factor that adjusts the result for enclosures larger or smaller than a 508 mm reference box, and an arcing-current variation correction factor for a mandatory second, lower-bound scenario. Because electrode configuration and enclosure size now change the answer materially, an arc flash study redone to IEEE 1584-2018 can differ substantially from a 2002 result for the same equipment — often higher for horizontal-electrode and barrier configurations. The ElecAS calculator uses the 2018 model throughout. #### Electrode configuration is the most important input IEEE 1584-2018 defines five electrode configurations, each with its own coefficient set: VCB (vertical electrodes in a metal box), VCBB (vertical electrodes terminated in an insulating barrier in a box), HCB (horizontal electrodes in a box), VOA (vertical electrodes in open air) and HOA (horizontal electrodes in open air). The configuration captures how the arc plasma is directed — a barrier or horizontal geometry pushes more energy toward the worker, so VCBB and HCB generally yield higher incident energy than VCB for the same fault. Box configurations (VCB, VCBB, HCB) apply the enclosure size correction factor, which adjusts the result for enclosures larger or smaller than the 508 mm × 508 mm × 508 mm reference box, and classify shallow enclosures (below 600 V, height and width under 508 mm, depth ≤ 203.2 mm) separately. Open-air configurations (VOA, HOA) take no enclosure correction. Choosing the configuration that matches the real equipment is the single biggest driver of an accurate result. #### Why arcing current and arc duration matter together The arcing current is not just an output — it is the current at which you read the upstream protective device to find the clearing time. IEEE 1584-2018 arcing current is typically 40–90% of the bolted fault current depending on voltage and configuration, and a lower arcing current can mean a longer clearing time on an inverse-time device, which increases incident energy. Because incident energy scales linearly with arc duration, an accurate clearing time matters as much as the current. IEEE 1584-2018 also requires a second scenario using a reduced arcing current (via the arcing current variation correction factor) to account for arc current variability — at the reduced current the device may clear more slowly, and the worst-case incident energy of the two scenarios governs. The ElecAS calculator reports both the average and the reduced arcing current so the two clearing times can be checked against the protective device curve. #### From incident energy to PPE and labels The incident energy in cal/cm² at the working distance is the number that drives arc-rated PPE selection — the PPE arc rating (ATPV or EBT) must equal or exceed it. The arc flash boundary defines where arc-rated protection becomes necessary. Common thresholds of 1.2, 4, 8, 25 and 40 cal/cm² band the result, and above 40 cal/cm² the blast hazard is severe enough that energised work should be avoided and the equipment de-energised. The incident energy result feeds the arc flash risk assessment and the equipment arc flash label. IEEE 1584-2018 gives the incident energy; the arc flash risk assessment, PPE program and labelling are governed by the applicable safety standard (such as NFPA 70E). This calculator is an engineering estimate to support that assessment — it does not replace it, and the results must be confirmed by a competent engineer against the actual protective-device coordination and site conditions. ## Voltage Rise Calculator — AS/NZS 4777.1 Solar PV & Inverter Compliance for Australia URL: https://elecas.com.au/calculator/voltage-rise Free, browser-based AS/NZS 4777.1 voltage rise calculator built for Australian solar PV designers, CEC accredited installers, electricians and electrical engineers. Models the full inverter-to-point-of-supply path — inverter AC cable, final subcircuit, submains and consumer mains — and applies the AS/NZS 4777.1 Clause 3.3.3 limit that the voltage rise from the point of supply to the inverter a.c. terminals must not exceed 2% of nominal voltage, calculated at the rated current of the IES (4.6 V on a 230 V single-phase system, 8 V line-to-line on a 400 V three-phase system). Supports single-phase and three-phase installations, multiple inverters with shared connection points, asymmetric per-inverter cable runs, worst-case power factor evaluation, export-limited systems, copper and aluminium conductors, V-90 / X-90 / V-75 PVC insulation, multi-core and single-core constructions, the full AS/NZS 3008.1.1 Table 3 installation method library, and the standard 2.5–630 mm² cable size range. Returns a per-segment voltage rise breakdown, total rise in volts and percent, a pass/fail pill against the 2% AS/NZS 4777.1 envelope, automatic suggestion of compliant cable sizes when a segment fails, and a branded PDF voltage rise compliance report ready for the DNSP / network operator submission. Who it is for: CEC accredited solar designers and installers, electrical contractors, distributed generation engineers and DNSP connection specialists checking the inverter-path voltage rise on residential, commercial and industrial solar PV and battery storage installations across Australia and New Zealand. Standards: AS/NZS 4777.1:2016 (Grid Connection of Energy Systems via Inverters — Installation Requirements, including Clause 3.3.3 voltage rise); AS/NZS 4777.2:2020 (Grid Connection of Energy Systems via Inverters — Inverter Requirements); AS/NZS 3000:2018 (Wiring Rules — Clause 3.6 voltage drop budget, Clause 7.3 alternative supply systems); AS/NZS 3008.1.1:2025 (Cable Selection — Tables 4.1–4.10 conductor R and X impedance values); AS/NZS 5033:2021 (Installation and Safety Requirements of Photovoltaic (PV) Arrays); AS 60038 (Standard Voltages — 230 V / 400 V nominal voltage used to express the rise as a percentage); AS/NZS 4509 (Stand-Alone Power Systems, where applicable) Key capabilities: - Applies the AS/NZS 4777.1:2016 Clause 3.3.3 inverter-path voltage rise limit — 2% of nominal voltage from the point of supply to the inverter a.c. terminals, calculated at the rated current of the IES and evaluated across every cable segment in the path. - Models the complete path the inverter sees back to the network: inverter AC cable, final subcircuit, submains and consumer mains, with the connection point selectable at the inverter, the final distribution board, the submain board or the main switchboard (MSB). - Supports multiple inverters per project — each with its own size, name and dedicated AC cable run — with results aggregated to a single compliance verdict so multi-inverter and string-inverter installations are sized correctly first time. - Single-phase (230 V) and three-phase (400 V) systems, with the calculator switching between line-to-neutral and line-to-line voltage rise automatically and supporting worst-case power factor evaluation for inverters operating at unity, leading or lagging PF. - Copper and aluminium conductors, multi-core and single-core constructions, V-75 PVC, V-90 PVC and X-90 XLPE insulation, and the standard 2.5 mm² to 630 mm² cable size range — all with impedance values read directly from AS/NZS 3008.1.1:2025 Tables 4.1 to 4.10. - Full AS/NZS 3008.1.1 Table 3 installation method library (M1–M11) — unenclosed in air, enclosed in conduit, buried direct and in underground enclosures — feeding the impedance lookup so the calculated rise matches the real install. - Auto-size assistant flags a failing segment and suggests the smallest standard cable size that brings the inverter-path rise back under the 2% AS/NZS 4777.1 limit, so over-sizing is only proposed where the compliance check requires it. - Export-limit aware — when the inverter is configured with a hard export limit the calculator uses the limited current for the rise calculation, avoiding the false fail that comes from using nameplate output on export-limited systems. - Branded PDF voltage rise compliance report with full project metadata (project name, number, address, designer, revision, date), single-line schematic of the inverter path, per-segment results and a pass/fail summary — ready for the DNSP / network connection application. - Built and reviewed by a Chartered Professional Engineer (CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE Aus) — see the Verification page for the testing and review process. How to use: How to calculate voltage rise for a solar PV inverter under AS/NZS 4777.1 1. Enter inverter sizes and number of inverters — Add each inverter with its continuous AC output in kilowatts. For string solar add one inverter per string; for multi-inverter systems add all inverters that share the same connection point so the calculator aggregates their current correctly. 2. Select phases and nominal system voltage — Set Phases to 1 (230 V single-phase) or 3 (400 V three-phase line-to-line / 230 V line-to-neutral). The calculator uses the AS 60038 nominal voltage to convert the per-segment rise into a percentage. 3. Set the connection point — Pick the consumer board the inverter electrically connects to — MSB (main switchboard), submain board, final distribution board, or directly at the inverter terminals. The calculator turns this into the sequence of cable segments the inverter current flows through back to the point of supply. 4. Enter each cable segment — For the inverter AC cable, final subcircuit, submain and mains, enter cable size (mm²), conductor (Cu or Al), construction (multi-core or single-core), insulation (V-75, V-90 or X-90) and length in metres. The calculator pulls R and X per kilometre from the AS/NZS 3008.1.1:2025 impedance tables (Tables 4.1–4.10). 5. Pick the installation method — Select the AS/NZS 3008.1.1 Table 3 installation method M1 to M11 that matches the physical install. The method controls which impedance row the tool reads and how the single-core arrangement (trefoil, flat-touching, flat-spaced) feeds into the reactance. 6. Set power factor and worst-case mode — Leave Use Worst-Case Power Factor on so the tool evaluates the inverter at the leading/lagging PF that produces the maximum AC current. Untick it only when the inverter is configured to operate at unity PF and you want the rise at PF = 1. 7. Apply export limit if configured — If the inverter has a hard export limit set by the DNSP connection agreement, switch on Export Limit and enter the limit in kW. The calculator uses the limited current — not nameplate — so the rise reflects the real continuous output. 8. Review the pass/fail and per-segment breakdown — Each segment shows its own voltage rise contribution and the total rise from the inverter terminals to the point of supply is compared against the 2% AS/NZS 4777.1 envelope. Where a segment fails the auto-size assistant suggests the smallest compliant cable size. 9. Export the branded PDF compliance report — Fill in the project metadata (project name, number, address, designer, revision, date) and export the voltage rise compliance report. Submit it with the DNSP / network connection application alongside the SLD and protection settings. ### AS/NZS 4777.1 voltage rise for solar PV — practical engineering guide #### What voltage rise is and why AS/NZS 4777.1 limits it When a grid-connected inverter exports active power, current flows back through the inverter AC cable, the final subcircuit, the submain and the consumer mains toward the point of supply. The IR + IX impedance of every conductor between the inverter and the network lifts the inverter terminal voltage above the nominal supply voltage. The rise is exactly the mirror image of voltage drop — same impedance values, same length, but in the opposite direction. AS/NZS 4777.1:2016 Clause 3.3.3 limits the rise from the point of supply to the inverter a.c. terminals to 2% of nominal voltage, calculated at the rated current of the IES. On a 230 V single-phase system the limit is 4.6 V; on a 400 V three-phase system the line-to-line limit is 8 V (or 4.6 V line-to-neutral). The reason the limit is tight is that the inverter monitors voltage at its own terminals: as the rise approaches the AS/NZS 4777.2 over-voltage trip point (255 V default on 230 V), the inverter starts curtailing output (volt-watt response), and a few volts of cable rise turns into kilowatt-hours of lost generation across a year. #### The 2% inverter path — what the limit actually covers The 2% limit applies to the entire inverter path from the inverter AC terminals back to the point of supply (the network connection point — typically the consumer mains origin / network meter). It is not a per-segment limit. The calculator therefore sums the rise on every cable in the path — inverter cable, final subcircuit (where the inverter does not connect directly at a board), submain and consumer mains — and compares the total against the 2% envelope. The connection point selector in the tool fixes which segments are in the path. An inverter connecting at the MSB only sees the consumer mains. An inverter connecting on a submain board sees the consumer mains plus that submain. An inverter on a final subcircuit sees mains plus submain plus final subcircuit plus its own AC tail. The current in each segment is the inverter export current at that point — for multi-inverter installations, segments downstream of the convergence carry only that inverter, while segments upstream of the convergence carry the aggregated current of every inverter on the same path. #### Single-phase vs three-phase behaviour For a single-phase inverter the voltage rise per segment uses ΔU = I × (R·cosφ + X·sinφ) × L where I is the rated current of the IES in amperes (per Clause 3.3.3), R and X are the AS/NZS 3008.1.1 resistance and reactance per metre, L is the route length in metres and φ is the operating power factor angle. The result is a per-segment rise in volts line-to-neutral, divided by 230 V to express it as a percentage. For a three-phase inverter the rise is √3 × I × (R·cosφ + X·sinφ) × L (line-to-line) for balanced three-phase output, with the percentage taken against 400 V. Three-phase inverters typically produce one-third the per-phase current of a single-phase inverter of the same kW rating, so the rise on the same cable run is roughly one-third — which is why moving from single-phase to three-phase is often the single most effective mitigation for marginal sites. #### Worst-case power factor and AS/NZS 4777.2 volt-var AS/NZS 4777.2:2020 requires inverters to provide reactive power response — volt-var, volt-watt, fixed PF and PF response modes. In an Australia A region default volt-var the inverter absorbs reactive power as terminal voltage rises (lagging from the grid’s perspective) and exports reactive when voltage falls. At the AS/NZS 4777.2 Australia A default, the inverter can be commanded to operate between roughly 0.8 leading and 0.8 lagging PF. The worst-case PF mode in the calculator scans the AS/NZS 4777.2 PF envelope and reports the rise at the PF that produces the maximum ΔU. For most cable runs this is the PF that puts cos φ + (X/R)·sin φ at a maximum — typically lagging on cables with significant reactance. Disabling worst-case mode evaluates at PF = 1.0, which is realistic only for inverters configured for unity PF operation with no volt-var. #### Mitigation hierarchy — cheapest fix first When a segment fails the 2% limit, work the mitigation ladder from cheapest to most disruptive. First, shorten the cable run — many failing installations are caused by an inverter mounted on the far side of the roof from the switchboard with an unnecessarily long AC cable. Second, increase the conductor cross-sectional area on the segment that contributes the largest absolute rise (the calculator’s per-segment table makes this obvious). Doubling the CSA roughly halves the rise on that segment. Third, switch from single-phase to three-phase where the supply allows — the same kW rating produces a third of the current, and the rise drops by a factor of three. Fourth, move the connection point upstream — moving an inverter from a final subcircuit to the submain board removes the final-subcircuit segment from the path entirely. Fifth, choose copper over aluminium for the inverter AC cable — copper has ~38% lower resistance per mm² so the rise on the inverter cable comes down by about a third for the same nominal size. Sixth, consider inverter clustering — running two smaller three-phase inverters at different boards instead of one large single-phase inverter at the final board halves the per-segment current. Seventh, request a network upgrade or tap change at the distribution transformer — only used when every other mitigation has been exhausted, because the DNSP timeline is months and the cost is borne by the customer. #### Export-limited systems and aggregated inverter current Many Australian DNSPs cap residential and small commercial export to 5 kW single-phase or 15 kW three-phase. By default AS/NZS 4777.1 Clause 3.3.3 requires the voltage rise to be calculated from the rated current of the IES, not a reduced export figure — the standard’s only relief is the note allowing the site’s known minimum load to be taken into account for an aggregate IES rating above 30 kVA. Where the DNSP connection agreement accepts sizing on a compliant AS/NZS 4777.2 hard export limit, the calculator’s Export Limit toggle applies the limited kW to the shared segments downstream of the export-limit measurement point; otherwise leave it off and size on the full IES rated current. For multi-inverter installations the rise on each segment uses the sum of the currents of every inverter whose path includes that segment. Two 5 kW single-phase inverters at the same final board both contribute their 21.7 A to the submain and mains, but only one contributes to its own AC tail. The tool aggregates the contributions automatically once each inverter’s connection path is set. #### Standards reference set and how the tool uses them AS/NZS 4777.1:2016 sets the inverter-path 2% rule (Cl. 3.3.3) and the installation requirements for grid-connected energy systems. AS/NZS 4777.2:2020 sets the inverter behaviour — over/under voltage trip points, volt-watt and volt-var response curves, anti-islanding and the rated output current that feeds the rise calculation. Conductor impedance comes from the AS/NZS 3008.1.1:2025 impedance tables (Tables 4.1 to 4.10), with the row chosen by conductor material, insulation operating temperature, construction (multi-core or single-core) and installation method. AS/NZS 3000:2018 Cl. 3.6 sets the separate load-side voltage drop budget (5% from the network, 7% from an on-site substation) — a parallel check handled by the ElecAS Voltage Drop calculator, not this inverter-path tool. AS 60038 fixes the nominal voltage (230 V single-phase, 400 V three-phase) used to express the rise as a percentage. AS/NZS 5033:2021 governs the DC array side and intersects with the AC side at the inverter. ### Frequently asked questions Q: What is the AS/NZS 4777.1 voltage rise limit for solar inverters in Australia? A: AS/NZS 4777.1:2016 Clause 3.3.3 requires that the voltage rise from the point of supply to the inverter a.c. terminals (the grid-interactive port) does not exceed 2% of the nominal voltage at the point of supply, calculated using the rated current of the IES. For 230 V single-phase that is 4.6 V; for 400 V three-phase that is 8 V line-to-line (or 4.6 V line-to-neutral). The limit applies to the entire inverter path — inverter cable plus any final subcircuit, submain and consumer mains in series back to the point of supply — not to each segment separately, and it applies in addition to the AS/NZS 3000 voltage drop requirements. Q: How is voltage rise calculated for a grid-connected solar PV inverter? A: Per AC cable segment ΔU = I × (R·cosφ + X·sinφ) × L for single-phase and ΔU = √3 × I × (R·cosφ + X·sinφ) × L for three-phase, where I is the rated current of the IES in amperes (AS/NZS 4777.1 Clause 3.3.3 specifies the rated current of the IES, not a reduced figure), R and X are the conductor resistance and reactance per metre from the AS/NZS 3008.1.1:2025 impedance tables (Tables 4.1–4.10) at the insulation operating temperature, L is the cable route length in metres, and φ is the inverter operating power factor angle. The segment rises are summed across every cable from the inverter to the point of supply, divided by nominal voltage, and compared against the 2% AS/NZS 4777.1 limit. Q: Does the 2% AS/NZS 4777.1 voltage rise limit include the consumer mains? A: Yes. AS/NZS 4777.1 Clause 3.3.3 measures the rise from the point of supply to the inverter a.c. terminals — the network connection point at the consumer mains origin. The consumer mains, submain, final subcircuit and inverter AC cable are all in that path, so their voltage rise contributions add together. Once you set the inverter connection point, the calculator includes every segment in the path automatically. Q: How do I reduce voltage rise on a solar PV installation that fails the 2% limit? A: Work the mitigation hierarchy from cheapest first: (1) shorten the AC cable run; (2) increase the cable cross-sectional area on the segment with the largest absolute rise — doubling CSA roughly halves rise on that segment; (3) switch from single-phase to three-phase inverters where supply allows (cuts current by ~3×); (4) move the inverter connection upstream (e.g. MSB instead of final board); (5) choose copper over aluminium for the inverter cable; (6) cluster smaller inverters across different boards; (7) request a DNSP tap change or feeder upgrade as a last resort. Q: Does an export-limited inverter still have to satisfy the 2% voltage rise limit? A: Yes — the 2% limit always applies. By default AS/NZS 4777.1 Clause 3.3.3 says the rise is calculated from the rated current of the IES, not a reduced export figure, so an export-limited inverter is still assessed at its rated current unless the network agreement says otherwise. The standard's one allowance is for an aggregate IES rating above 30 kVA, where the site's known minimum load may be taken into account. Where your DNSP accepts a compliant AS/NZS 4777.2 hard export limit for the rise calculation, the calculator's Export Limit toggle applies the limited kW to the shared segments downstream of the export-limit measurement point; otherwise size on the full IES rated current. Q: How does the calculator handle multiple inverters on the same installation? A: Add each inverter with its own size, name, AC cable run and connection point. The tool aggregates currents per segment — every inverter whose path crosses a given segment contributes its export current to that segment, so the upstream consumer mains carries the sum of all inverters while each inverter's own AC tail carries only its own current. The final pass/fail verdict checks the worst-case inverter path against the 2% AS/NZS 4777.1 limit. Q: What is the difference between voltage drop and voltage rise? A: Voltage drop occurs on cables supplying loads (current flows consumer-mains to load) and is governed by AS/NZS 3000:2018 Cl. 3.6.2 with a 5% total budget (7% from an on-site substation). Voltage rise occurs on cables exporting from generation (current flows inverter to point of supply) and is governed by AS/NZS 4777.1:2016 Cl. 3.3.3 with a 2% inverter-path limit. The same cable on the same install has both — drop under maximum demand and rise under maximum export — but they are assessed separately: this calculator covers the AS/NZS 4777.1 inverter-path voltage rise, while the ElecAS Voltage Drop calculator covers the load-side drop. Q: Should I use worst-case power factor for AS/NZS 4777.1 voltage rise? A: Yes, where the inverter is configured for any AS/NZS 4777.2 reactive response mode (volt-var, fixed PF other than unity, PF response). Worst-case PF evaluates the rise at the operating PF that maximises ΔU = I × (R·cosφ + X·sinφ) × L, which is typically lagging on cables with non-trivial reactance. Disable worst-case only when the inverter is locked to PF = 1.0 by the DNSP connection agreement and the network operator has accepted unity-PF compliance. Q: Does AS/NZS 4777.1 require a combined voltage drop and voltage rise check? A: Not as a single combined calculation. AS/NZS 4777.1 Clause 3.3.3 states that its 2% voltage rise requirement applies in addition to the voltage drop requirements of AS/NZS 3000, so the two are assessed separately and both must be satisfied — the AS/NZS 3000 load-side drop (up to 5%) under maximum demand, and the 2% inverter-path rise under maximum generation. The underlying aim is to keep the consumer's utilisation voltage inside the AS 60038 range, with the point of supply held at or below 253 V (230 V +10%). This calculator covers the AS/NZS 4777.1 inverter-path voltage rise only; for the load-side drop and maximum demand use the ElecAS Voltage Drop and Maximum Demand calculators. Q: What cable size do I need for a 5 kW single-phase solar inverter to satisfy the 2% voltage rise limit? A: A 5 kW single-phase inverter exports about 21.7 A continuous at 230 V. The minimum compliant cable depends entirely on the total length of every segment between the inverter and the point of supply. As a guide: under ~10 m total path a 4 mm² copper cable typically passes; 10 to 25 m needs 6 mm² to 10 mm² copper; 25 to 50 m typically needs 16 mm² copper. The ElecAS calculator returns the actual smallest standard size after applying the AS/NZS 3008.1.1 impedance values and the AS/NZS 4777.1 2% limit to your specific install. Q: Does cable temperature affect voltage rise? A: Yes. AS/NZS 3008.1.1:2025 publishes its conductor impedance tables (Tables 4.1 to 4.10) at the maximum continuous operating temperature of each insulation class — 75 °C for V-75 PVC, 90 °C for V-90 PVC, X-90 XLPE and R-90 elastomer, and 110 °C for X-110 XLPE and R-110 elastomer. Resistance rises ~0.4% per °C in copper, so an XLPE inverter cable at 90 °C exhibits a few percent more rise than the same conductor sized in V-75 PVC. The ElecAS calculator selects the correct temperature row automatically based on the chosen insulation. Q: Can I use aluminium cable for solar inverter AC connections? A: Yes — aluminium is permitted under AS/NZS 3000 for solar inverter AC cables, particularly on larger commercial systems where the mains and submain are already aluminium. Aluminium has roughly 1.6× the resistance of copper for the same cross-section, so it contributes more voltage rise per metre and is restricted to V-75, V-90 and X-90 insulation (no 110 °C aluminium is manufactured in Australia). Always confirm aluminium-rated terminations on the inverter, isolator and switchboard — many smaller residential inverters specify copper-only terminations. ## Cable Size Calculator — AS/NZS 3008.1.1:2025 Cable Sizing for Australia URL: https://elecas.com.au/calculator/cable-selection Free, browser-based AS/NZS 3008.1.1:2025 cable size calculator built for Australian electrical engineers, designers, electricians, estimators and contractors. Enter your design current, supply phase, conductor material, insulation, construction, installation method, route length and protection device — the calculator returns the smallest compliant cable size after running every check that AS/NZS 3000 and AS/NZS 3008.1.1 require: current-carrying capacity with k1 ambient, k2 grouping, k3 soil thermal resistivity and k4 depth-of-burial derating; protection coordination Ib ≤ In ≤ Iz; voltage drop against your per-segment limit and the AS/NZS 3000 Clause 3.6.2 envelope (5%, with the customary 7% design allocation where supply is from an on-site substation); device breaking capacity against the prospective fault current; the I²t ≤ k²S² adiabatic short-circuit withstand check on both the active and the earth conductor using AS/NZS 3008.1.1:2025 Table 5.1 k-values (111.2 Cu/PVC, 142.9 Cu/XLPE, 73.7 Al/PVC, 94.6 Al/XLPE), with the earth conductor checked at both ends of the run; and earth-fault loop impedance computed from the full R + jX cable loop per the AS/NZS 3000 Appendix B4 framework, with the trip current Ia pulled directly from the linked Schneider Electric circuit protection database (Im for thermal-magnetic MCBs and MCCBs, Ii for electronic-trip MCCBs and ACBs). Three conductor types — Copper (Cu), Copper Flexible, Aluminium (Al) — and five insulation classes — V-75 PVC, X-90 XLPE, R-90 elastomeric, X-110 XLPE and R-110 elastomeric (the calculator's essential-safety / fire-rated option per AS/NZS 3013) — are supported, along with the full AS/NZS 3008.1.1 Table 3 installation method library M1 to M11. Auto insulation resolves V-75 up to 16 mm² and X-90 above for a chosen size (auto-sizing assumes X-90), construction Auto resolves multi-core up to 95 mm² and single-core from 120 mm² upward, and R-110 is selected manually for fire-rated and essential-services sections. Built-in support for parallel runs, separate earth-conductor sizing per Table 5.1, full project metadata capture and a branded PDF cable selection report you can drop straight into a design submission. Who it is for: Electrical engineers, designers, electricians, estimators and contractors sizing copper, copper flexible or aluminium conductors for consumer mains, submains, final subcircuits, motor circuits and essential / fire-rated services under AS/NZS 3000:2018, AS/NZS 3008.1.1:2025, AS/NZS 3013 and the National Construction Code (NCC). Standards: AS/NZS 3008.1.1:2025 (Cable Selection — Tables 3.9–3.20 capacity, 3.33–3.48 derating, 4.1–4.10 impedance, 5.1 k-values); AS/NZS 3000:2018 (Wiring Rules, including Clauses 2.5.3, 3.4, 3.6, 5.7.2 and Appendix B4); AS/NZS 3000 Table 5.1 (Earthing Conductor Sizing); AS/NZS 3000 Table 8.1 (Maximum Earth-Fault Loop Impedance); AS/NZS 3013 (Fire-Rated Wiring Systems — WS Classification); AS 60038 (Standard Voltages — 230 V +10% / -6%); National Construction Code (NCC) — essential services Key capabilities: - Runs every AS/NZS 3000 and AS/NZS 3008.1.1:2025 cable selection check in one pass — current carrying capacity (with full k1·k2·k3·k4 derating), Ib ≤ In ≤ Iz protection coordination, voltage drop, breaking capacity, I²t ≤ k²S² thermal withstand on the active and the earth conductor, and earth-fault loop impedance. - Applies the four AS/NZS 3008.1.1 correction factors automatically from Tables 3.33–3.48 — ambient air or soil temperature (k1), grouping (k2), soil thermal resistivity (k3) and depth of burial (k4) — and shows the resulting Total Derating Factor in the configuration panel. - Three conductor options — Copper (Cu), Copper (Flexible) and Aluminium (Al) — with calculator-aware impedance values for fine-stranded flexible cores and the aluminium-specific insulation restrictions. - Five insulation classes — V-75 PVC, X-90 XLPE, R-90 elastomeric, X-110 XLPE, and R-110 elastomeric (the essential-safety / fire-rated option for fire pumps, mechanical essential boards, fire-mode lifts and fire detection / EWIS per AS/NZS 3013). - Auto insulation picks V-75 PVC up to 16 mm² and X-90 XLPE above for a chosen size (auto-sizing assumes X-90), and construction Auto picks multi-core up to 95 mm² and single-core from 120 mm² upward — the same conventions used on Australian commercial and industrial installations. R-110 elastomeric is selected manually for fire-rated sections. - Ten construction layouts covering single-phase and three-phase: 2C+E, 2C, 2x1C+E, 2x1C, 4C+E, 3C+E, 4C, 4x1C+E, 3x1C+E and 4x1C — with the calculator counting loaded conductors when it pulls the AS/NZS 3008.1.1 capacity table. - Full AS/NZS 3008.1.1 Table 3 installation method library — unenclosed in air (M1–M4), enclosed in conduit (M5–M8), buried direct (M9) and in underground enclosures (M10–M11) — with single-core arrangement options (trefoil, flat-touching, flat-spaced) feeding the impedance lookup. - Voltage drop calculated by the impedance method Z = √(R² + X²) per AS/NZS 3008.1.1, with a one-toggle switch to the actual-PF projection Vc = R·cosφ + X·sinφ for tighter sizing on known-PF loads, and the per-segment limit checked against your design split (typically 1% mains, 1.5–2% submains, 2–2.5% final subcircuits inside the 5% Cl. 3.6.2 envelope, or the customary 7% substation allocation). - Earth-fault loop impedance computed from the full cable impedance loop Zs = Ze + √((R_loop·L)² + (X_loop·L)²) per the AS/NZS 3000 Appendix B4 framework, with the trip current Ia pulled from the linked Schneider Electric circuit protection database (Im for MCB / thermal-magnetic MCCB, Ii for electronic-trip MCCB / ACB) and a fuse fallback when no breaker record applies. - Native parallel-runs support per AS/NZS 3000 Cl. 3.4.3 with a separate earth conductor stepper, automatic AS/NZS 3000 Table 5.1 earth sizing, and a project metadata block (project name, number, address, designer, revision) that flows into the exported PDF cable selection report. - Built and reviewed by a Chartered Professional Engineer (CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE Aus) — see the Verification page for the testing and review process. How to use: How to size a cable under AS/NZS 3008.1.1 and AS/NZS 3000 1. Enter design current (Ib) — Enter the maximum continuous design current the circuit will carry. For motors use the nameplate full-load current; for distribution circuits use the maximum demand from AS/NZS 3000 Section 2. 2. Select phases and protection device — Set Phases to 1 or 3 and pick the upstream protective device (MCB curve B/C/D, MCCB, ACB or fuse). The device rating In must satisfy Ib ≤ In ≤ Iz per AS/NZS 3000 Cl. 2.5.3.1. 3. Choose conductor, insulation and construction — Pick Copper (Cu), Copper Flexible or Aluminium; pick V-75, X-90, R-90, X-110 or R-110 insulation (or leave Auto); pick a multi-core or single-core construction with the appropriate number of cores for the loading. 4. Choose AS/NZS 3008.1.1 installation method — Select Method M1–M4 (unenclosed in air), M5–M8 (enclosed in conduit), M9 (buried direct) or M10–M11 (in underground enclosure) to match the physical install. 5. Apply derating factors — Switch on Apply Derating and enter ambient temperature, number of grouped circuits, soil thermal resistivity and depth of burial. The calculator pulls k1·k2·k3·k4 from AS/NZS 3008.1.1 Tables 3.33–3.48 automatically. 6. Set route length and voltage drop budget — Enter the cable route length in metres and the per-segment voltage drop allowance — typically 1% for consumer mains, 1.5–2% for submains and 2–2.5% for final subcircuits, inside the AS/NZS 3000 Cl. 3.6.2 5% envelope (or the customary 7% substation allocation). 7. Enter fault current and clearing time — Provide the prospective short-circuit current Isc at the cable origin and the upstream device clearing time so the calculator can run the adiabatic I²t ≤ k²S² check on the active and the earth conductor. 8. Set external impedance Ze for Zs check — Enter the supply external impedance Ze (default 0.35 Ω for residential or 0.02 Ω for an on-site substation). The calculator computes Zs = Ze + √((R_loop·L)² + (X_loop·L)²) from the full cable impedance and verifies Zs ≤ U₀/Ia against the AS/NZS 3000 Cl. 5.7.2 disconnection time. 9. Review pass/fail pills and export the PDF report — Each compliance check shows a pass/fail pill. When every check passes, fill in the project metadata block and export the branded PDF cable selection report for submission. ### Cable sizing under AS/NZS 3008.1.1:2025 — practical guide #### Standards and methodology The ElecAS cable size calculator reads tabulated values directly from the current Australian/New Zealand standards — no rules of thumb and no interpolation beyond the published data. AS/NZS 3008.1.1:2025 is the dominant reference: current-carrying capacity comes from the Section 3 tables (Tables 3.9 to 3.20 for the supported constructions) selected by the chosen installation method, conductor and insulation; voltage drop uses the impedance values published in Tables 4.1 to 4.10 (R and X per kilometre at the conductor operating temperature); derating factors come from Tables 3.33 to 3.48; and short-circuit k-values for the adiabatic check come from Table 5.1. AS/NZS 3000:2018 (the Wiring Rules) drives the compliance checks. Clause 2.5.3.1 sets protection coordination Ib ≤ In ≤ Iz. Clause 3.4.1 and Table 3.3 fix minimum conductor sizes. Clause 3.4.3 governs parallel runs. Clause 3.6.2 sets the 5% voltage drop limit from the point of supply (a 7% allocation is a common design convention where supply is from an on-site substation). Appendix B4 frames the earth-fault loop impedance requirement — the tool computes the full R + jX loop rather than the resistance-only shortcut. Clause 5.7.2 sets disconnection times (0.4 s for socket-outlet final subcircuits up to 63 A, hand-held Class I and portable equipment; 5 s for other circuits). Table 5.1 fixes the minimum earthing conductor and Table 8.1 publishes the corresponding maximum Zs values. AS 60038 sets the nominal voltage envelope (230 V +10% / −6%) that the 5% drop limit feeds into. #### The six compliance checks Cable selection requires more than one check. The calculator verifies current-carrying capacity with correction factors, voltage drop, short-circuit thermal withstand and earth-fault loop impedance/disconnection time. It also verifies protection coordination per AS/NZS 3000 Cl. 2.5.3.1 (Ib ≤ In ≤ Iz) and short-circuit breaking capacity at the device. Each check is reported with its own pass/fail pill in the result summary. Capacity is the cable’s tabulated rating after the four derating factors are applied (ambient temperature k1, grouping k2, soil thermal resistivity k3 and depth of burial k4). The thermal withstand uses the adiabatic equation I²t ≤ k²S² on both the active and the earth conductor with the Table 5.1 k-value matched to the resolved insulation, and the earth conductor is checked for a fault at both ends of the run. The earth-fault loop impedance check computes the full impedance loop Zs = Ze + √((R_loop·L)² + (X_loop·L)²) and verifies Zs ≤ U₀ / Ia for the disconnection time required by Cl. 5.7.2. #### Voltage drop split across the path AS/NZS 3000:2018 Cl. 3.6.2 limits the total drop from the point of supply to any load to 5% of nominal when the supply comes from the network — 11.5 V on a 230 V single-phase circuit and 20 V line-to-line on a 400 V three-phase circuit. Where the point of supply is at a consumer-owned on-site substation, designers commonly allocate up to 7% — a design convention rather than a figure published in Cl. 3.6.2. The total is a budget for the whole path. A conservative allocation that gives sensible headroom at the final outlet is roughly 1.0% on consumer mains, 1.5% to 2.0% on submains, and 2.0% to 2.5% on final subcircuits. The calculator’s Maximum Voltage Drop field is the per-segment limit you want this cable checked against. #### Conductor, insulation and construction choices Copper is the default in Australia. Aluminium is offered for large mains and submains (typically 70 mm² and above) where weight and cost favour it, but it has only ~60% of copper’s conductivity, cold-flows under terminal pressure, oxidises and reacts galvanically with copper. The calculator restricts the insulation menu to V-75, X-90 and R-90 when aluminium is selected because the 110 °C products are only manufactured in copper. V-75 PVC is the calculator’s default for lighting, general power and small submains; the Auto rule selects V-75 for any size up to 16 mm². X-90 XLPE carries roughly 25–30% more current in the same cross-section with a higher Table 5.1 k-value (142.9 vs 111.2); Auto selects X-90 once the resolved cable is larger than 16 mm². The deciding factor in practice is termination temperature — most MCBs, switch-disconnectors and lug terminals are rated for 75 °C terminations, so even an X-90 cable has to be sized off the 75 °C column at those devices. R-110 elastomeric is the calculator’s fire-rated option (R-HF-110 / R-E-110 halogen-free elastomeric circuit-integrity cables) — pick it manually from the Insulation selector for essential-services sections. Construction Auto resolves to multi-core up to 95 mm² and single-core from 120 mm² upwards, with the earth integral by default. #### Derating and installation methods Switch the Apply Derating toggle on and the four AS/NZS 3008.1.1 correction factors fold in automatically: k1 for ambient air or soil temperature (Tables 3.44 and 3.45), k2 for grouping of circuits (Tables 3.33 to 3.43), k3 for soil thermal resistivity on buried cables (Table 3.48), and k4 for depth of burial (Tables 3.46 and 3.47). Their product is the Total Derating Factor shown in the configuration panel — typically between 0.5 and 1.0 in real installations. AS/NZS 3008.1.1 publishes the entire buried current carrying capacity table at a reference resistivity of 1.2 K·m/W. Most moist Australian soils sit around 1.5 K·m/W, dry sandy soils run 2.0 to 2.5 K·m/W, and crushed-rock or thermally enhanced sand can go below 1.0 K·m/W. Use the geotechnical report value or 1.5 K·m/W as a conservative default. The Installation Method selector matches the AS/NZS 3008.1.1 method codes to the physical install. Unenclosed in air (M1–M4) covers tray, ladder or clipped direct; Enclosed in conduit (M5–M8) covers surface or in-wall conduit; Buried direct (M9) covers cables in a trench; and In underground enclosure (M10–M11) covers cables in buried conduits or ducts. Buried installations do not automatically mean smaller cables. #### Short-circuit thermal withstand and earth-fault loop impedance Short-circuit withstand tends to govern when prospective fault currents are high and the upstream protection has a relatively slow clearing time. Typical clearing-time presets are about 10 ms for an HRC fuse, 20 ms for a current-limiting MCB, 40 ms for a standard MCCB, 80 ms for an electronic-trip MCCB and 100 ms for an ACB. The adiabatic equation I²t ≤ k²S² is applied to both the active and the earth conductor with k from AS/NZS 3008.1.1:2025 Table 5.1: 111.2 for copper PVC (≤300 mm²; 98.5 above), 142.9 for copper 90 °C XLPE/elastomer, 131.8 for the copper 110 °C classes, 73.7 for aluminium PVC and 94.6 for aluminium XLPE. The earth conductor is checked for a fault at both ends of the run. For earth-fault loop impedance the calculator implements the AS/NZS 3000 Appendix B4 framework with the full cable impedance: Zint = √((R_loop·L)² + (X_loop·L)²) / 1000, Zs = Ze + Zint, and the pass condition is Zs ≤ U₀ / Ia with U₀ = 230 V. The trip current Ia is read from the linked Schneider Electric circuit protection database — Im for MCBs and thermal-magnetic MCCBs, Ii for electronic-trip MCCBs and ACBs, with a generic fuse fallback when no breaker record applies. #### Earth conductor sizing and parallel runs The minimum copper protective earthing conductor comes from AS/NZS 3000 Table 5.1. The calculator’s Earth Conductor selector defaults to Auto and follows the table: 1, 1.5 and 2.5 mm² actives keep an earth equal to the active; from 4 to 10 mm² the earth steps down (4 and 6 mm² actives resolve to 2.5 mm² earth, a 10 mm² active to 4 mm²); from 16 mm² upwards the earth is roughly half the active CSA (50 → 16 mm², 95 → 25 mm², 150 → 50 mm², 240 → 95 mm²). Table 5.1 caps the copper earth at 120 mm² for 400–630 mm² actives (25% of the active above 630 mm²); the calculator keeps the half-size convention there, which exceeds that minimum. With aluminium actives Table 5.1 permits a smaller copper earth at the same active size. Table 5.1 is only the minimum — the earth still has to pass the adiabatic check I²t ≤ k²S² at both ends of the run and the Zs loop check, which the calculator runs automatically, upsizing the earth (never beyond the active size) if needed. For parallel runs, set the Parallel Runs stepper to the number of identical sets and the design current per run becomes Ib / n. AS/NZS 3000 Cl. 3.4.3 requires every run to be no smaller than 4 mm² and identical in length, cross-sectional area, conductor material and installation method. Parallel single-core runs are usually grouped and may also need the AS/NZS 3008.1.1 Tables 3.33–3.43 grouping factor. #### Fire-rated and essential-services cables A fire-rated cable keeps circuit integrity for a specified period under fire exposure so the load it feeds keeps operating from the mains during evacuation. AS/NZS 3013 publishes the wiring system (WS) classification — e.g. WS52W combines a 1100 °C fire test with water spray and mechanical impact. Fire rating is required where the load has no autonomous backup and must keep drawing mains power during the fire — fire pumps and sprinkler controls (AS 2941, AS 4214), mechanical services essential boards, emergency / fire-mode lifts, fire detection and EWIS / sound systems where the head-end has no on-board battery (AS 1670, AS 7240), and any other circuits the NCC designates as essential (Specification E1.5 / E2.2). Emergency and exit luminaires (AS/NZS 2293) and the FIP have integral batteries and do not require fire-rated cables. The support system has to hold the cable in place for the full WS-rated duration. AS/NZS 3013 calls for stainless-steel ties or metallic clips, reduced fixing spacings of about 350 mm or less, tested fire-rated cleats matched to the cable family, and heavy-gauge steel trays with documented fire test results. Penetrations through fire-rated walls or floors must use a tested seal. ### Frequently asked questions Q: What standards does the ElecAS cable size calculator use? A: AS/NZS 3008.1.1:2025 supplies the current carrying capacity tables (Section 3 — Tables 3.9 to 3.20 for the supported constructions), derating factors (Tables 3.33 to 3.48), conductor R and X values for voltage drop (Tables 4.1 to 4.10) and short-circuit k-values (Table 5.1). AS/NZS 3000:2018 drives compliance — Cl. 2.5.3.1 protection coordination, Cl. 3.4 minimum sizes, Cl. 3.6.2 voltage drop limit (5% from the point of supply; a 7% allocation is a common design convention where supply is from an on-site substation), Cl. 5.7.2 disconnection times, the Appendix B4 earth-fault loop framework, Table 5.1 earth conductor sizing and Table 8.1 maximum Zs. AS/NZS 3013 covers fire-rated wiring systems and AS 60038 sets the 230 V +10% / -6% voltage envelope. Q: What checks does the cable size calculator run? A: Six checks on every result: (1) current carrying capacity after k1·k2·k3·k4 derating; (2) protection coordination Ib ≤ In ≤ Iz per AS/NZS 3000 Cl. 2.5.3.1; (3) voltage drop against your per-segment limit and the Cl. 3.6.2 envelope; (4) device breaking capacity against the prospective fault current; (5) the adiabatic I²t ≤ k²S² short-circuit thermal withstand check on both the active and the earth conductor using AS/NZS 3008.1.1:2025 Table 5.1 k-values, with the earth checked at both ends of the run; and (6) earth-fault loop impedance computed from the full R + jX cable loop, Zs = Ze + √((R·L)² + (X·L)²), against the Cl. 5.7.2 disconnection time. Q: How much voltage drop is allowed under AS/NZS 3000, and how do I split it across consumer mains, submain and final subcircuit? A: AS/NZS 3000:2018 Cl. 3.6.2 limits the total drop from the point of supply to any load to 5% of nominal when the supply comes from the network — 11.5 V on a 230 V single-phase circuit and 20 V line-to-line on a 400 V three-phase circuit. Where the point of supply is at a consumer-owned on-site substation, designers commonly allocate up to 7% — a design convention rather than a figure published in Cl. 3.6.2. The total is a budget for the whole path, not a per-segment limit. A conservative allocation is roughly 1.0% on consumer mains, 1.5% to 2.0% on submains, and 2.0% to 2.5% on final subcircuits. The calculator’s Maximum Voltage Drop field is the per-segment limit checked against this cable. Q: What voltage drop limit applies to consumer mains in Australia? A: AS/NZS 3000 Cl. 3.6.2 does not publish a separate limit for consumer mains — the 5% total (or the customary 7% allocation from an on-site substation) applies from the point of supply to the load. Designers conventionally hold the mains segment to roughly 1.0% so the submain and final subcircuit downstream still have room to comply. The calculator checks whatever per-segment allowance you enter and the result still has to satisfy the appliance operating-voltage range once it is combined with the rest of the path. Q: Does cable temperature affect voltage drop? A: Yes — copper resistance rises about 0.4% per °C, and AS/NZS 3008.1.1 publishes its impedance tables (Tables 4.1 to 4.10) at the maximum continuous operating temperature of each insulation class. The calculator picks the correct row automatically once you select the insulation: 75 °C values for V-75 PVC, 90 °C values for X-90 XLPE and R-90 elastomer, and 110 °C values for X-110 XLPE and R-110 elastomer. Voltage drop on a fully loaded XLPE cable is therefore a few percent worse than the same conductor sized in PVC because the conductor is hotter at design current. Q: Should I use worst-case PF or the actual power factor for voltage drop? A: AS/NZS 3008.1.1 publishes two methods and the calculator offers both via the Worst Case PF toggle. With it on (the default) the cable component is the full impedance Zc = √(R² + X²) — conservative and bounded regardless of the load plant that ends up connected, suitable for distribution boards, mains and mixed loads. With the toggle off the calculator uses the actual-PF projection Vc = R·cosφ + X·sinφ from the entered power factor; real loads at lagging PF give a smaller drop than the worst-case envelope, allowing tighter sizing where the load PF is known and stable (a single dedicated motor, VFD or large fixed plant). Q: How is voltage drop calculated for single-phase vs three-phase cables? A: The base formula is the same: Vd = (L × Ib × Vc) / 1000, with L in metres, Ib in amps and Vc the cable’s mV/A·m factor. What changes is the multiplier baked into Vc to account for the loop. On single-phase circuits the current returns through the neutral, so Vc = 2·Z. On three-phase line-to-line drop the geometry gives Vc = √3·Z. The calculator picks the correct factor automatically from the Phases selector at the top of the configuration panel. Q: What size cable do I need for a 32A circuit in Australia? A: For a single-phase 32 A circuit in copper V-75, the AS/NZS 3008.1.1:2025 tables give 4 mm² unenclosed (34–37 A spaced or touching) but 6 mm² enclosed in conduit (Method M5 — 4 mm² tabulates 30 A enclosed, just short of 32 A). A three-phase 32 A circuit derates further because three conductors are loaded, and longer runs or tighter voltage-drop allowances often push the result up a size. Re-run the calculator for your actual phasing, length, ambient temperature and grouping, then verify short-circuit withstand and Zs against the upstream device. Q: What size cable do I need for a 63A circuit? A: Reference: copper, three single-cores in conduit on a wall (Method M5), per the AS/NZS 3008.1.1:2025 tables. V-75 PVC copper lands at 25 mm² for capacity (16 mm² tabulates 62 A, just short of 63 A); X-90 XLPE copper drops to 16 mm² (10 mm² tabulates 56 A), subject to terminal temperature ratings. Buried installations do not automatically mean smaller cables: direct-buried (M9) only outperforms M5 at the AS/NZS 3008.1.1 reference soil resistivity of 1.2 K·m/W and shallow burial. Most Australian soils sit at 1.5–2.5 K·m/W which derates buried capacity significantly, and buried-in-enclosure (M10) ratings are often similar to or lower than M5. Re-run the calculator with your actual soil resistivity, depth and grouping. Q: What size cable do I need for a 100A submain? A: A 100 A copper submain typically falls around 25–35 mm² depending on installation method, insulation type, conductor arrangement and derating. Three single-core copper V-75 cables in conduit on a wall (Method M5) land at 35 mm², which tabulates exactly 100 A at reference conditions (no headroom for derating). Aluminium will generally require a larger size (around 70 mm² in the same scenario since 50 mm² aluminium tabulates 92 A in M5). Voltage drop becomes the governing constraint on long runs or where the upstream allowance is tight. Q: What size cable for a 200A consumer mains? A: Reference: three single-cores in conduit on a wall (Method M5), per the AS/NZS 3008.1.1:2025 tables. Copper V-75 PVC lands at 120 mm² for capacity (95 mm² tabulates 183 A); copper X-90 XLPE drops to 95 mm² at 220 A (70 mm² tabulates 183 A), subject to terminal temperature ratings; aluminium V-75 PVC steps up to 185 mm² (150 mm² tabulates 190 A and 120 mm² only 169 A in M5). Voltage drop on long mains often governs — keep this segment to about 1% allowance to leave room for the submain and final subcircuit. Q: How do I derate a cable for grouping and ambient temperature? A: Switch the Apply Derating toggle on and the calculator pulls all four AS/NZS 3008.1.1 correction factors at once: k1 for ambient air or soil temperature (Tables 3.44 and 3.45), k2 for grouping of circuits (Tables 3.33 to 3.43), k3 for soil thermal resistivity on buried cables (Table 3.48) and k4 for depth of burial (Tables 3.46 and 3.47). Their product is the Total Derating Factor shown in the configuration panel — typically between 0.5 and 1.0 in real installations. The calculator sizes the cable so Iz_actual = Iz_table × k1 × k2 × k3 × k4 stays at or above the design current Ib. Q: When does grouping derating apply? A: Grouping derating from AS/NZS 3008.1.1 Tables 3.33 to 3.43 applies whenever multiple loaded cables run in close proximity — bunched in a conduit, on a tray, in an enclosed run or tied together — because each cable raises the temperature of its neighbours and reduces the heat the conductor can dissipate. Switch on the Grouping sub-toggle, set the Number of Circuits to the actual number of loaded circuits in the group, and pick the matching arrangement (bunched in air, single layer on a tray, multilayer, or buried) — the calculator pulls the correct factor and folds it into k2. Spacing of at least one cable diameter between adjacent cables avoids the derating entirely on most installation methods. Q: Why does soil thermal resistivity matter for buried cables? A: A buried cable dissipates the heat from its losses through the surrounding soil. The higher the soil’s thermal resistivity, the more poorly it conducts that heat away, and the hotter the cable runs at any given current. AS/NZS 3008.1.1 publishes the entire buried current carrying capacity table at a reference resistivity of 1.2 K·m/W; Table 3.48 gives the k3 correction for any value above or below that. Most moist Australian soils sit around 1.5 K·m/W, dry sandy soils run from 2.0 to 2.5 K·m/W, and crushed-rock backfill or thermally enhanced sand can go below 1.0 K·m/W. Use the geotechnical report value or 1.5 K·m/W as a conservative default. Q: Which AS/NZS 3008.1.1 installation method should I select? A: The Installation Method selector matches the AS/NZS 3008.1.1 method codes to the physical install. Pick Unenclosed in air (Methods M1 to M4) for cables on a tray, ladder or clipped direct to a wall, with sub-options for spaced or touching arrangements; Enclosed in conduit (Methods M5 to M8) for surface or in-wall conduit and trunking; Buried direct (Method M9) for cables laid in a trench with controlled backfill; and In underground enclosure (Methods M10 to M11) for cables drawn into buried conduits or ducts. Buried installations do not automatically mean smaller cables — buried direct only outperforms an in-air install at reference resistivity and shallow burial. Q: Copper vs aluminium — which conductor should I size with? A: Copper is the default in Australia. It has higher conductivity for the same cross-section, better mechanical and fatigue strength, and terminates cleanly into standard lugs without specialist preparation. Aluminium is genuinely useful on large mains and submains (typically 70 mm² and above) where lower weight and cost outweigh the drawbacks, but it has only ~60% of copper’s conductivity (one or two sizes larger for the same current), cold-flows under terminal pressure demanding torque-controlled lugs and anti-oxidation paste, oxidises with a poorly-conducting oxide layer, and reacts galvanically with copper so any aluminium-to-copper joint needs a bimetallic lug. The calculator restricts the insulation menu to V-75, X-90 and R-90 when aluminium is selected because the 110 °C products are only manufactured in copper. Q: V-75 (PVC) vs X-90 (XLPE) — which insulation should I pick? A: V-75 PVC runs at 75 °C and is the cheapest construction; the calculator’s Auto rule selects V-75 for any size up to 16 mm². X-90 XLPE runs at 90 °C, carries roughly 25 to 30% more current in the same cross-section, and has a higher Table 5.1 k-value (142.9 vs 111.2 for copper) — Auto selects X-90 once the resolved cable is larger than 16 mm². The deciding factor in practice is termination temperature: most MCBs, switch-disconnectors and lug terminals are rated for 75 °C terminations, so even an X-90 cable has to be sized off the 75 °C column at those devices. Q: What is cable insulation and what does it do? A: The insulation is the dielectric layer surrounding each conductor. It prevents leakage between conductors and to earth at the operating voltage, sets the maximum continuous conductor temperature (which together with the installation method fixes the AS/NZS 3008.1.1 current carrying capacity), and sets the short-circuit k-value used in the Table 5.1 adiabatic check. The five Australian insulation classes are V-75 (PVC 75 °C), X-90 (XLPE 90 °C including X-90UV and X-HF-90 halogen-free variants), R-90 (Elastomeric 90 °C including R-EP-90, R-CPE-90 and R-HF-90), X-110 (XLPE 110 °C, X-HF-110 form), and R-110 (Elastomeric 110 °C, R-HF-110 and R-E-110 forms — the fire-rated option). The 110 °C options are only available with copper conductors. Q: How do I select the right cable insulation? A: Leave the Insulation selector on Auto and the calculator resolves V-75 PVC up to 16 mm² and X-90 XLPE above 16 mm² for a manually selected size (auto-sizing assumes X-90 since the size is not known yet) — the same convention most contractors and suppliers default to. For fire-rated and essential-services sections, pick R-110 elastomeric manually. Pick V-75 manually for general dry fixed wiring at 40 °C indoor ambients. Pick X-90 when capacity is tight, ambient is elevated, the run is heavily grouped, or you want the ~25 to 30% capacity uplift. Pick R-90 elastomeric for industrial, vibration-prone or harsh-environment runs. Pick X-110 when 90 °C XLPE is still capacity-limited. Pick R-110 for fire-rated and critical-service circuits. Always verify the terminal temperature rating of the upstream and downstream device. Q: How do I choose the number of cores for a cable? A: The Construction selector filters automatically once you set Phases. Single-phase offers four constructions: 2C+E (active, neutral, integral earth), 2C (active and neutral with a separate earth), 2x1C+E and 2x1C single-cores. Three-phase offers six: 4C+E (three actives, neutral, integral earth — for any submain or consumer main feeding single-phase loads), 3C+E (three actives plus earth — balanced three-phase loads such as motors), 4C (separate earth), and the corresponding single-core layouts (4x1C+E, 3x1C+E, 4x1C). Auto resolves to multi-core up to 95 mm² and single-core from 120 mm² upwards, with the earth integral by default. Q: Single-core vs multi-core cables — which should I pick? A: Multi-core cables carry every conductor inside one outer sheath, which is easier to install, identify and terminate, fits cleanly through conduits, and ensures the conductors take the same path. The calculator’s Auto rule picks multi-core for any cable up to 95 mm². Single-core cables run each conductor in its own jacket — Auto switches to this from 120 mm² upwards because multi-core becomes physically unwieldy at those sizes and parallel runs (which AS/NZS 3000 Cl. 3.4.3 only allows on identical single-cores) become more common. For single-cores the Cable Arrangement selector lets you pick trefoil, flat-touching or flat-spaced; the calculator pulls the correct R and X values from the matching AS/NZS 3008.1.1 impedance table. Q: What is a fire-rated cable, and when is it required? A: A fire-rated cable keeps circuit integrity for a specified period (typically 30, 60, 90 or 120 minutes) under fire exposure so the load it feeds keeps operating from the mains during evacuation. AS/NZS 3013 publishes the wiring system (WS) classification — e.g. WS52W combines a 1100 °C fire test with water spray and mechanical impact. Fire rating is required where the load has no autonomous backup and must keep drawing mains power during the fire — fire pumps and sprinkler controls (AS 2941, AS 4214), mechanical services essential boards, emergency / fire-mode lifts, fire detection and EWIS / sound systems where the head-end has no on-board battery (AS 1670, AS 7240), and any other circuits the NCC designates as essential (Spec E1.5 / E2.2). Emergency and exit luminaires (AS/NZS 2293) and the FIP have integral batteries and do not require fire-rated cables. The ElecAS calculator sizes fire-rated cables as 110 °C elastomeric (R-110). Q: Do I need a fire-rated cable tray or support system? A: Yes. When the circuit is fire-rated the support system has to hold the cable in place for the full WS-rated duration — standard galvanised tray or PVC saddles lose structural integrity in minutes and the cable will fall before its insulation fails. AS/NZS 3013 calls for stainless-steel ties or metallic clips (PVC ties are prohibited), reduced fixing spacings of about 350 mm or less, tested fire-rated cleats matched to the cable family, and heavy-gauge steel trays with documented fire test results. Penetrations through fire-rated walls or floors must use a tested seal (intumescent collar, mortar or pillow) so the wall’s FRL is preserved. The fire-resisting integrity is only as good as the weakest link — cable, support, fixing, penetration seal and termination must all carry the specified rating. Q: What is the WS classification on a cable, and what does it mean? A: WS stands for Wiring System under AS/NZS 3013, and the code summarises three combined tests applied to the entire system rather than the cable alone. The W component is the fire test (subscript X = no fire, Y = lower-temperature exposure, Z = full 1100 °C exposure), the S component is the water-spray test, and the trailing numeral is the mechanical impact rating. Common designations on Australian projects include WS51W and WS52W (1100 °C fire combined with water spray and mechanical impact, longer duration on WS52W) and WS3X (mechanical impact only, no fire). The project’s fire engineering report specifies the required WS rating per circuit, and the cable, support system, cleats and terminations all have to meet or exceed that rating. Q: When is short-circuit thermal withstand the limiting factor? A: Short-circuit withstand tends to govern when prospective fault currents are high (close to the supply transformer or downstream of a large on-site substation) and the upstream protection has a relatively slow clearing time. The calculator’s Source Fault Current field carries the prospective Isc at the location of the cable, and Fault Clearing Time is the duration the protection takes to interrupt that fault — typical presets are about 10 ms for an HRC fuse, 20 ms for a current-limiting MCB, 40 ms for a standard MCCB, 80 ms for an electronic-trip MCCB and 100 ms for an ACB. The check is the adiabatic equation I²t ≤ k²S² on both the active and the earth conductor (the earth is checked for a fault at both ends of the run), with k from AS/NZS 3008.1.1:2025 Table 5.1: 111.2 for copper PVC (≤300 mm²; 98.5 above), 142.9 for copper 90 °C XLPE/elastomer, 131.8 for the copper 110 °C classes, 73.7 for aluminium PVC and 94.6 for aluminium XLPE. Q: How does the calculator check earth-fault loop impedance under AS/NZS 3000? A: The calculator implements the AS/NZS 3000 Appendix B4 earth-fault loop framework using the full cable impedance: Zint = √((R_loop·L)² + (X_loop·L)²) / 1000, where R_loop and X_loop sum the active and earth conductor values per kilometre at operating temperature (on small cables this reduces to the familiar resistance-only method). The total loop impedance is Zs = Ze + Zint, with Ze the external impedance of the supply (presets from 0.02 Ω at an on-site substation MSB to 0.35 Ω at a residential final circuit). The pass condition is Zs ≤ U₀ / Ia with U₀ = 230 V and Ia from the linked Schneider Electric breaker database — Im for MCBs and thermal-magnetic MCCBs, Ii for electronic-trip MCCBs and ACBs, with a generic fuse fallback. The disconnection time required by Cl. 5.7.2 is 0.4 s for socket outlets up to 63 A and portable equipment, and 5 s for fixed and distribution circuits. Q: What size earth conductor do I need? A: The minimum copper protective earthing conductor comes from AS/NZS 3000 Table 5.1. The calculator’s Earth Conductor selector defaults to Auto and follows the table: 1, 1.5 and 2.5 mm² actives keep an earth equal to the active; from 4 to 10 mm² the earth steps down (4 and 6 mm² actives resolve to 2.5 mm² earth, a 10 mm² active to 4 mm²); from 16 mm² upwards the earth is roughly half the active CSA (50 → 16 mm², 95 → 25 mm², 150 → 50 mm², 240 → 95 mm²). Table 5.1 caps the copper earth at 120 mm² for 400–630 mm² actives (25% of the active above 630 mm²); the calculator keeps the half-size convention there, which exceeds that minimum. With aluminium actives Table 5.1 permits a smaller copper earth at the same active size. Table 5.1 is only the minimum — the earth still has to pass the adiabatic check I²t ≤ k²S² at both ends of the run and the Zs loop check, which the calculator runs automatically, upsizing the earth (never beyond the active size) if needed. Q: What is the smallest cable allowed under AS/NZS 3000? A: Minimum conductor sizes depend on the circuit type, conductor material, wiring system and mechanical protection. From AS/NZS 3000:2018 Table 3.3 and common Australian practice: lighting final subcircuits are typically 1.0 mm² copper minimum, and socket-outlet final subcircuits are typically 2.5 mm² copper minimum. Signal and relay control circuits can drop to 0.5 mm² and flexible cords to 0.75 mm²; aerial wiring is 6 mm² copper or 16 mm² aluminium. Submains and consumer mains are not in Table 3.3 — their size is driven by capacity, voltage drop, short-circuit withstand and Zs, but practical minimums still apply (consumer mains typically not less than 16 mm² copper or 25 mm² aluminium under most utility service rules). The calculator’s standard size set runs from 1 mm² to 630 mm² in the AS/NZS 3008 preferred series. Q: How do I size a cable for a three-phase motor? A: Take the motor full-load current from the nameplate (not the locked-rotor or starting current — protection device coordination handles those transients) and enter it into the Design Current field. For continuous-duty motors a common convention is to size on roughly 1.25 × FLA to allow for sustained running, but the actual design current depends on duty cycle, overload protection, starting method, installation conditions and the AS/NZS 3000 Section 4 motor requirements. Set Phases to 3 and Construction to 3C+E or 3x1C+E (no neutral for a balanced three-phase motor). Voltage drop on the longest motor run is usually the governing constraint, especially for soft-started or VFD-fed motors where excessive volt drop also worsens torque output and starting performance. Q: How do I handle parallel cable runs? A: Set the Parallel Runs stepper to the number of identical sets and the design current per run becomes Ib / n; the calculator picks a cable that, multiplied back by n, satisfies the loading. AS/NZS 3000 Cl. 3.4.3 (capacity) and Cl. 3.6.3 (voltage drop) require every run to be no smaller than 4 mm² and identical in length, cross-sectional area, conductor material and installation method, which ensures the current actually shares evenly. The earth conductor has its own parallel-runs stepper. Parallel single-core runs are usually grouped and may also need the grouping derating from AS/NZS 3008.1.1 Tables 3.33 to 3.43 — switch on Apply Derating and the calculator pulls the matching factor automatically. Q: Which MCB protective device curve should I use — B, C or D? A: The MCB curve sets the magnetic instantaneous trip threshold the calculator uses for its earth-fault loop impedance check. Curve B trips at 3–5× In and suits resistive loads and lighting. Curve C trips at 5–10× In and is the general-purpose default. Curve D trips at 10–20× In and is reserved for transformers, motors and other loads with high inrush that would nuisance-trip a C curve. The compliance trade-off comes through Ia in Zs ≤ U₀ / Ia: a higher curve raises Ia, which lowers the maximum permissible Zs and tightens the earth-fault loop impedance constraint. If a C-curve passes Zs and a D-curve does not, you usually need to drop a curve, increase the cable size to lower Zs, or switch to an electronic-trip device. Q: Does the calculator handle four-core cables and neutral derating? A: Yes. The Construction selector covers four single-phase layouts (2C+E, 2C, 2x1C+E, 2x1C) and six three-phase layouts (4C+E, 3C+E, 4C, 4x1C+E, 3x1C+E, 4x1C). For a balanced three-phase load with no neutral — most three-phase motors — pick a 3C+E or 3x1C+E construction; for any submain feeding single-phase loads downstream pick a 4C+E or 4x1C+E so a neutral is included. The calculator counts loaded conductors when it pulls the AS/NZS 3008.1.1 capacity table — three loaded actives in a 4C+E cable are rated lower than two loaded actives in a 2C+E. Where the load is harmonic-rich (LED lighting, drives, IT equipment), AS/NZS 3008.1.1 requires the neutral to be treated as a current-carrying conductor; keep a 4C construction and accept the four-loaded-conductor rating. Q: Is the ElecAS cable size calculator free? A: Yes — the AS/NZS 3008.1.1:2025 cable size calculator runs entirely in your browser, with no account required for the standard workflow, and the cable selection report exports as a PDF you can attach to the project documentation. Project metadata (project name, number, address, designer, revision) is captured at the top of the page and flows into the exported report so the PDF is ready to issue. ## Cable Correction Factor Calculator URL: https://elecas.com.au/calculator/correction-factor Apply ambient, grouping, soil and installation condition factors to cable current-carrying calculations. Who it is for: Users adjusting cable current-carrying capacity for temperature, grouping and installation environment. Standards: AS/NZS 3008 Key capabilities: - Review ambient, grouping and soil-related derating factors. - Support cable selection decisions with environment-specific adjustments. - Move directly to cable sizing once correction factors are understood. How to use: How to apply cable derating factors under AS/NZS 3008.1.1:2025 1. Set the installation method — Pick the AS/NZS 3008.1.1 installation method (A, B, C, D, E, F or G — corresponding to enclosed in conduit, on a wall, in a tray, direct buried, in free air, etc.). The installation method selects which Table 3–13 base rating to use. 2. Enter the number of circuits in the grouping — Enter the number of cable circuits in the same enclosure / on the same tray / in the same trench. The calculator picks the Table 22–24 / 27 / 29 grouping factor. 3. Enter the ambient temperature — Enter the design ambient air temperature in °C. The calculator picks the Table 25–26 temperature factor for the matching insulation type. 4. For buried installations, enter the soil thermal resistivity — Enter the soil thermal resistivity in K·m/W (reference is 1.2 for moist clay; sandy / dry soils are higher). The calculator picks the Table 3.48 factor. 5. Review the composite factor and derated rating — The calculator displays each individual factor with its table reference, the composite (multiplied) factor, and the derated current-carrying capacity. Export the branded PDF. ### Cable current-carrying-capacity derating under AS/NZS 3008.1.1:2025 #### Why current-carrying capacity must be derated The tabulated current-carrying capacities in AS/NZS 3008.1.1:2025 Tables 3–13 are based on a single circuit in free air or in a reference installation method at 30 °C ambient. Real installations almost always deviate from those reference conditions: cables are grouped, ambient air temperature differs, soil thermal resistivity differs, and direct-buried installations need a separate suite of corrections. AS/NZS 3008.1.1:2025 Tables 3.33–3.48 publish derating factors for each deviation. The final derated current-carrying capacity is the tabulated value multiplied by the product of all applicable derating factors. Failure to apply derating is one of the most common AS/NZS 3000 compliance non-conformances flagged during certification. #### The four derating dimensions Grouping (Table 22–24): cables installed in the same enclosure, on the same tray, or in the same buried duct bank derate each other. Factors range from 1.00 for a single circuit to about 0.40 for 20+ grouped circuits. Ambient air temperature (Table 25–26): for ambient temperatures above 30 °C (typical engine room, ceiling void, switchboard cabinet) the factor reduces. For V-90 PVC the 45 °C factor is 0.79; for X-90 XLPE the factor is 0.85. Soil thermal resistivity (Table 3.48): the reference soil resistivity is 1.2 K·m/W (moist clay). Dry or sandy soils have higher resistivity (2.5–3.0 K·m/W) and the corresponding factor is 0.80–0.65. Direct-buried grouping (Table 27, 29): cables in the same trench or duct bank derate each other; the spacing between cables drives the factor. #### How the ElecAS derating calculator combines factors All applicable factors are multiplied together to give a composite derating factor. The derated current-carrying capacity is then the Table 3–13 base rating multiplied by this composite. The branded PDF report lists every factor applied with its table reference so the calculation can be audited row-by-row. The calculator integrates with the ElecAS cable selection calculator: when sizing a cable, the derating factors apply before the design current is checked against the rating. This avoids the common error of selecting a cable on its undertated tabulated rating only to find it non-compliant once grouping is applied. ### Frequently asked questions Q: What is a cable correction factor? A: A correction factor is a multiplier applied to a cable's base current-carrying capacity to account for installation conditions that differ from the reference conditions in AS/NZS 3008.1.1 — typically ambient temperature, grouping, soil thermal resistivity and depth of burial. Q: How do I combine multiple correction factors? A: Multiply the factors together: derated capacity = base capacity × k1 × k2 × k3 × k4. The result must remain at or above the design current. Q: When does grouping derating apply? A: Grouping derating from AS/NZS 3008.1.1 Tables 22–24 applies when multiple loaded cables are installed touching or in close proximity (in trays, conduits, or enclosed runs). Spacing of at least one cable diameter between cables can avoid the derating. Q: When do I need to apply derating factors to AS/NZS 3008 cable ratings? A: Whenever the installation deviates from the reference conditions of the Section 3 base-rating tables: more than one circuit grouped together, ambient above the 40 °C air / 25 °C soil reference, soil resistivity above 1.2 K·m/W, or direct buried with closely spaced circuits. The applicable factors from Tables 3.33–3.48 are multiplied together. Q: What is the AS/NZS 3008 derating factor for 4 cables in a conduit? A: For 4 multicore circuits enclosed in a single conduit, AS/NZS 3008.1.1:2025 Table 22 gives a grouping factor of 0.65 (for 3 or more conductors per circuit). For single-core circuits installed in trefoil the factor is different — refer to Table 23. Q: How does ambient temperature affect cable rating? A: For ambient temperatures above the 30 °C reference, the Table 25–26 factor reduces. At 40 °C the V-90 PVC factor is 0.87; at 45 °C it is 0.79; at 50 °C it is 0.71. X-90 XLPE factors are higher because the insulation temperature limit is higher. Q: Do I apply derating before or after the cable selection check? A: Derating is applied to the tabulated current-carrying capacity FIRST, then the derated capacity is compared to the design current. Applying derating after a cable selection (i.e., sizing on the unrated capacity and then "checking" derating) is the most common AS/NZS 3000 compliance non-conformance. ## Conduit Sizing Calculator URL: https://elecas.com.au/calculator/conduit-sizing Free Australian conduit sizing calculator. Pick from real Prysmian and Olex cable catalogue data, mix cores and sizes, and get the smallest compliant HD-PVC conduit with parallel-run packing and a branded PDF report. Who it is for: Electrical engineers, contractors, designers and installers sizing HD-PVC, medium-duty and heavy-duty conduits for AS/NZS 3000:2018 compliance in Australian and New Zealand projects. Standards: AS/NZS 3000:2018 — Electrical installations (Wiring Rules), Appendix C / Tables C10–C12; AS/NZS 3008.1.1:2025 — Electrical installations, selection of cables, Tables 22–24 (grouping factors); AS/NZS 5000.1 — Electric cables — Polymeric insulated, voltages up to and including 0.6/1 kV; IEC 60364-5-52 — Selection and erection of wiring systems (equivalent fill guidance); NEC Chapter 9 Table 1 — fill-percentage source for 1/2/3+ cable rule of thumb Key capabilities: - Auto AS/NZS-aligned space factor: 50% for 1 cable, 33% for 2 cables, 40% for 3+ cables — conservative industry rule of thumb against AS/NZS 3000:2018 Appendix C Tables C10–C12. - Real product catalogue: 380+ Prysmian Australia and Olex (Prysmian Group) cables with manufacturer-published outer diameter and mass. - Distinguishes flat TPS, round multicore, XLPE multicore, SDI single-core and SWA steel-wire-armoured cables — same nominal spec but different OD and fill. - Mixed-cable bin packing (best-fit decreasing) with automatic parallel-run distribution when no single conduit fits. - Cross-sectional sketches to scale and a branded PDF report citing AS/NZS 3000:2018 Appendix C for every run. - Coverage for 20 mm, 25 mm, 32 mm, 40 mm, 50 mm, 63 mm, 80 mm, 100 mm, 125 mm and 150 mm HD-PVC conduit nominal sizes. - Catalogue references (Prysmian SKUs and Olex codes) embedded in the run schedule so the PDF is unambiguous for procurement. How to use: How to size a conduit for AS/NZS 3000:2018 1. Pick the cable manufacturer — Choose Prysmian Australia or Olex (Prysmian Group) so the calculator filters to that catalogue. Both are tagged with manufacturer in the product database. 2. Choose a cable family — Select the construction family — PVC Insulated single core, PVC Multicore Circular, XLPE Multicore Circular, PVC/XLPE SWA armoured, SDI single-core, Versolex flex or Envirolex halogen-free. The family determines outer diameter and mass. 3. Pick the cable size and quantity — Choose the nominal conductor area (1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 630 mm²) and how many cables of that type are running through the conduit. 4. Set the space factor — Leave auto on to apply the AS/NZS-aligned 50% / 33% / 40% rule, or override manually if your specification requires a different fill (some clients require 35% maximum, particularly for harsh-environment runs). 5. Set the maximum enclosure size — Cap the largest HD-PVC nominal you are willing to install (e.g. 100 mm). The calculator falls back to parallel runs of this maximum size when a single conduit cannot fit the bundle. 6. Review the recommendation and export the PDF — The output shows the chosen conduit nominal, average fill percentage, run schedule and to-scale cross-section. Export a branded AS/NZS 3000:2018 Appendix C compliance PDF with catalogue references for procurement. ### Complete guide to conduit sizing under AS/NZS 3000:2018 #### What does AS/NZS 3000:2018 Appendix C say about conduit fill? AS/NZS 3000:2018 Appendix C provides count-based selection tables (Tables C10, C11 and C12) for the maximum number of single-core, two-core-and-earth and four-core-and-earth cables permitted in standard medium-duty and heavy-duty UPVC conduit nominal sizes. The tables embed a space factor implicitly and account for cable pulling friction, conductor expansion under load and field installation tolerances. For mixed bundles, designers fall back to an area-based rule of thumb recognised in IEC 60364-5-52 and common Australian engineering practice: 50% maximum fill for a single cable, 33% for two cables, and 40% for three or more cables. This rule is conservative against the AS/NZS count tables for almost every common cable family. The ElecAS conduit sizing calculator uses the area-based approach so it can handle any mix of cable types — flat TPS, round multicore, XLPE single-core SDI, steel-wire armoured (SWA), flexible Versolex and halogen-free Envirolex — that the AS/NZS count tables do not directly cover. #### Why outer diameter (and not conductor size) drives conduit selection Conduit fill is a geometric problem, not an electrical one. A 25 mm² copper conductor inside a thin V-90 PVC sheath has a very different outer diameter to the same conductor inside an XLPE/SWA/PVC armoured construction. Catalogue OD for the latter can be 50% larger, and the area inside the conduit it occupies scales with diameter squared. The calculator reads outer diameter directly from the manufacturer catalogue (Prysmian Australia Technical Cable Guide and Olex Cable Handbook), so flat TPS, round multicore and SWA variants of the same 2C+E 1.5 mm² CU PVC nominal correctly resolve to three different fill outcomes. #### How the area-based packing algorithm works Cables are flattened from quantities into individual items, sorted by outer diameter descending, and packed bin-by-bin using a best-fit-decreasing heuristic. Each cable is assigned to the least-filled conduit run that still has room within the fill limit. When a single conduit cannot fit the bundle, the algorithm switches to parallel runs of the user-selected maximum nominal size and distributes the cables evenly. The area-based check is conservative against geometric circle packing: the jamming limit for identical circles inside a circular container is approximately 78%, and even with mixed sizes the practical achievable packing rarely exceeds 60%. Fill limits of 40% therefore leave significant geometric headroom for real-world pulling tolerances and field bends. #### When to apply grouping derating in addition to fill checks Cables enclosed in conduit are derated for grouping under AS/NZS 3008.1.1:2025 Tables 22–24 in addition to satisfying the AS/NZS 3000 Appendix C fill check. Fill alone is a containment check; it does not address the reduced heat dissipation inside the conduit. For 3-core-and-earth and 4-core-and-earth multicore cables drawing 80% or more of their rating, designers typically apply a grouping factor of 0.8–0.9 for two-circuit enclosed runs, dropping to 0.7 or lower for six or more circuits in the same conduit. The ElecAS cable selection calculator handles the derating side; the conduit sizing calculator handles the containment side, and the two are intended to be used together. #### Manufacturer catalogue coverage The calculator ships with 380+ cable products mapped from the Prysmian Australia Technical Cable Guide (October 2015 edition) and the Olex (Prysmian Group) Cable Handbook (2017 edition). Coverage includes V-90 PVC and X-90 XLPE single-core and multicore families, PVC-bedded steel-wire armoured (SWA) variants, single-core double-insulated (SDI), Versolex flex (XLPE/TPE) and Envirolex halogen-free (XLPE/HFS RE-110). Every product carries its manufacturer catalogue reference (Prysmian SKU or Olex code), so the exported AS/NZS 3000:2018 Appendix C compliance PDF includes a procurement-ready run schedule with the exact cable model installed in each conduit. ### Frequently asked questions Q: What is the maximum conduit fill ratio in Australia under AS/NZS 3000? A: AS/NZS 3000:2018 Appendix C provides count-based selection in Tables C10, C11 and C12. For mixed cable bundles the calculator uses an equivalent area-based rule of thumb: 50% for a single cable, 33% for two cables, and 40% for three or more cables. This is conservative against the AS/NZS count tables for almost every cable family. Q: How do I size conduit for mixed cable sizes? A: Sum the cross-sectional area of all cables (use π × OD² / 4 per cable based on the manufacturer outer diameter, not conductor size) and select the smallest conduit whose internal area gives a fill ratio at or below the AS/NZS 3000 Appendix C limit for that cable count. The ElecAS conduit sizing calculator does this automatically and handles mixed Prysmian and Olex catalogue products. Q: Does AS/NZS 3000:2018 require derating for cables in conduit? A: Yes. AS/NZS 3000 Appendix C governs the geometric fill check; AS/NZS 3008.1.1:2025 Tables 22–24 require an additional grouping derating factor for cables enclosed in conduit because heat dissipation is reduced. Typical derating factors are 0.8–0.9 for two enclosed circuits and 0.7 or lower for six or more. The ElecAS cable selection calculator applies the derating side automatically. Q: What conduit size do I need for 4 × 25 mm² 4-core-and-earth XLPE cables? A: A single 100 mm HD-PVC at roughly 21% fill, or a 125 mm at roughly 14% fill, will accommodate 4 × XLPE 4C+E 25 mm² Cu multicore (outer diameter ~23 mm per cable) under the 40% area limit for 3+ cables. Use the ElecAS conduit sizing calculator to confirm against your specific cable catalogue (SWA armoured variants are significantly larger). Q: Why are flat TPS and round multicore the same spec but different conduit fill? A: A 2C+E 1.5 mm² CU PVC flat twin-and-earth has an outer cross-section of about 10.1 × 4.6 mm. The equivalent round multicore is 10.1 mm circular. The flat cable occupies less conduit area but more conduit width — both matter for pulling tolerance, and the calculator uses the largest dimension to stay conservative. Q: Does the ElecAS calculator support steel-wire armoured (SWA) cables? A: Yes. The Prysmian and Olex SWA multicore families (2C+E, 3C+E, 4C+E in PVC and XLPE) are included with their published outer diameters. SWA armoured cables of the same nominal conductor size have outer diameters 40–60% larger than the unarmoured equivalent, so the resulting conduit recommendation often steps up one or two nominal sizes. Q: Is the conduit sizing PDF report compliant with AS/NZS 3000:2018? A: The PDF report cites AS/NZS 3000:2018 Appendix C, shows the applied fill limit, lists the cables packed into each run with manufacturer catalogue reference, and includes a to-scale cross-sectional sketch. The report is a documented design check intended to support the responsible electrical engineer; final verification and field tolerance remain with the certifying engineer. Q: Is this conduit sizing calculator free to use? A: Yes. The full conduit sizing calculator is free to use online with no sign-up required. The branded PDF report (with company logo, designer name and accent colour) is included in the free tier. Cloud project sync and team workspaces are paid Pro / Team features. ## Cable Tray Sizing Calculator URL: https://elecas.com.au/calculator/cable-tray Free Australian cable tray sizing calculator. Pick from real Prysmian and Olex cable catalogue data, choose flat or trefoil arrangements, touching or spaced layouts, and get the smallest compliant tray with tier allocation and a branded PDF report. Who it is for: Electrical engineers, designers, contractors and project drafters sizing ladder and perforated cable trays for AS/NZS 3000:2018 installations, sub-mains and mains cable runs in industrial, commercial and infrastructure projects across Australia and New Zealand. Standards: AS/NZS 3000:2018 — Electrical installations (Wiring Rules), wiring systems; AS/NZS 3008.1.1:2025 — Electrical installations, selection of cables, Tables 22–24 (grouping factors) and Tables 25–27 (touching vs spaced arrangements); AS/NZS 5000.1 — Electric cables — Polymeric insulated, voltages up to and including 0.6/1 kV; IEC 60364-5-52 — Selection and erection of wiring systems (cable management); Manufacturer tray load curves (e.g. EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil) for span-based safe working load Key capabilities: - Pick from 380+ Prysmian Australia and Olex (Prysmian Group) cable products with manufacturer-published outer diameter and mass — no hand-typed approximations. - Flat (touching), flat (spaced), trefoil (touching) and trefoil (spaced) layouts on a per-cable basis — mix arrangements within the same tray. - Trefoil width = 2 × cable diameter geometry, with automatic grouping of three matching single-core cables per circuit. - Reserve capacity allowance (default 20%) applied per-tier so each tier preserves spare room for future cables. - Multi-tier allocation when the smallest tray cannot fit the bundle — packs cables into stacked tiers up to the user-defined maximum tray width. - Cable mass in kg/m per tier so designers can cross-check against tray manufacturer span-load curves (EzyStrut, Unistrut, Legrand Cablofil, Cooper B-Line). - Standard nominal widths: 50, 75, 100, 150, 225, 300, 450, 600, 750 and 900 mm — the common Australian tray product ladder. - Branded PDF report with cable schedule, tier allocation and to-scale cross-section, with manufacturer catalogue references embedded for procurement. How to use: How to size a cable tray for AS/NZS 3000:2018 1. Pick the cable manufacturer — Filter the catalogue to Prysmian Australia or Olex (Prysmian Group). The mass per metre and outer diameter feed both the width calculation and the tray-load weight estimate. 2. Choose a cable family — Select the construction family for each cable on the tray. SWA armoured cables, SDI single-core and flex variants all have different outer diameters and masses; the calculator applies the right values automatically. 3. Pick the layout method per cable — Flat (touching) packs cables shoulder-to-shoulder, flat (spaced) adds a configurable diameter gap, trefoil (touching) groups three matching single-cores into an equilateral triangle of width 2D, and trefoil (spaced) adds a gap between trefoil groups. 4. Set the spacing factor for spaced layouts — For AS/NZS 3008.1.1:2025 Tables 25–27 derating relief, spacing must be at least one cable diameter. Set spacingFactor = 1.0 for touching avoidance, or 2.0–3.0 if your specification requires more. 5. Set reserve capacity and maximum tray width — Reserve is the future-cable allowance (commonly 20–50% in industrial fit-outs). The maximum tray width caps the largest single tier the calculator may select; beyond that limit the calculator stacks tiers. 6. Review the recommendation and export the PDF — The output shows recommended tray nominal width, tier count, mass per metre, used width and a cross-section sketch. Export the PDF for the design pack; cross-check the mass against the tray vendor span-load curve. ### Complete guide to cable tray sizing for AS/NZS 3000:2018 projects #### Geometry — why flat and trefoil arrangements have different tray widths Three identical single-core cables of diameter D packed in a touching trefoil form an equilateral triangle of side D. The bounding rectangle is 2D wide and (D + D × √3/2) ≈ 1.87D tall. The calculator therefore consumes 2D of tray width per trefoil group, versus 3D of tray width if the same three cables were laid flat and touching. Trefoil reduces tray width but increases tray depth requirement. For spaced arrangements, an additional gap of one or more cable diameters between adjacent cables (or between trefoil groups) is required to obtain AS/NZS 3008.1.1:2025 Table 26 grouping factor relief. Spacing of 1D between flat cables typically restores 80–90% of the ungrouped current rating; spacing of 2D essentially eliminates grouping derating. #### AS/NZS 3008.1.1 grouping derating and tray-layout decisions Cables laid touching in a single layer on a tray are derated under AS/NZS 3008.1.1:2025 Table 22 (multi-core) or Table 23 (single-core). The derating factor drops from 1.00 for a single circuit to around 0.85 for three circuits and 0.70 for six or more circuits in the same touching layer. Tables 25–27 then offer relief when cables are spaced — by at least one cable diameter for adjacent single-core, or one trefoil width for trefoil groups. The trade-off is direct: spaced layouts use more tray width but allow smaller cable sizes (less derating), and touching layouts use less tray width but force larger cables (more derating). The ElecAS calculator handles the geometry side; the ElecAS cable selection calculator handles the current-rating side. #### Reserve capacity — what value to pick Industry practice for greenfield commercial fit-outs in Australia is 25–50% reserve capacity on cable trays, with 20% common for tight retrofit and infrastructure projects. Reserve allows for future cable adds without re-trunking the building. The ElecAS calculator applies reserve as a per-tier multiplier on usable width, so each populated tier preserves the same reserve fraction. For mission-critical installations (data centres, hospitals, defence) clients frequently mandate 100% reserve or N+1 redundancy. Set the reserve field accordingly and use the maximum tray width limit to cap the largest single tier; the calculator will stack tiers if the bundle exceeds that cap. #### Tray load — cable mass per metre and tray span The calculator reads cable mass per 100 m directly from the Prysmian and Olex catalogues and converts to kg/m for each tier. Compare the tier mass against the tray manufacturer span-load curve — typical perforated tray ratings range from 25 kg/m at 3 m support span to 75 kg/m at 1.5 m, with heavy-duty ladder trays reaching 200 kg/m at short spans. AS/NZS 3000:2018 does not publish numeric tray load limits — those come from the tray vendor (EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil). The ElecAS PDF includes total mass per metre and per-tier mass so the responsible engineer can perform the vendor check. #### Standard cable tray sizes in Australia Cable tray products from Australian distributors typically follow the 50, 75, 100, 150, 225, 300, 450, 600, 750 and 900 mm nominal width ladder. The calculator selects the smallest tray whose actual width accommodates the raw cable bundle plus reserve. Trays wider than 900 mm exist (e.g. 1200 mm splitable into two 600 mm trays) but are uncommon outside utility and substation environments. Depth nominally 50 mm for light-duty perforated tray; 75–100 mm for medium-duty ladder; 150 mm and above for heavy-duty cable ladder carrying high-voltage cables. The calculator outputs width only — depth selection follows the largest cable OD and the chosen layout (trefoil bundles need more depth than flat formations). #### When to use cable tray, conduit or ladder Cable tray (perforated and ladder) is preferred for sub-mains, mains and submains feeders inside plant rooms, risers and ceiling spaces where pulling tolerance, future modification and ventilation matter more than mechanical protection. Conduit (HD-PVC, medium-duty) is preferred for final subcircuits and exposed runs where mechanical protection, water ingress and aesthetics dominate. For mixed installations — tray on the riser, conduit on the floor — the ElecAS conduit sizing calculator and cable tray sizing calculator share the same Prysmian and Olex catalogue so cable picks remain consistent across both reports. ### Frequently asked questions Q: How do I choose cable tray width for Australian electrical installations? A: Sum the outer diameter of every cable to be installed, allowing for AS/NZS 3008.1.1:2025 spacing if your design requires grouping derating relief, add a future-capacity reserve (commonly 20–50%), then select the smallest standard tray nominal width (50, 75, 100, 150, 225, 300, 450, 600, 750 or 900 mm) that fits the result. The ElecAS cable tray sizing calculator does this automatically using real Prysmian and Olex catalogue data. Q: How do I calculate trefoil cable tray width? A: A touching trefoil group of three identical single-core cables of diameter D occupies a tray width of 2D (the bounding rectangle of an equilateral triangle of side D). For spaced trefoil groups, add the spacing factor multiplied by D between groups. The ElecAS cable tray sizing calculator groups three matching single-cores into trefoil automatically when the trefoil layout method is selected. Q: Should cables on a tray be touching or spaced? A: Touching arrangements use less tray width but trigger AS/NZS 3008.1.1:2025 Table 22 / 23 grouping derating, forcing larger conductor sizes. Spacing cables by at least one diameter (per Tables 25–27) eliminates most of the derating but uses more tray width. The right trade-off depends on load currents, available real estate and cable cost. For sub-mains carrying near-rated currents, spacing is usually worth the extra tray width. Q: Does cable tray sizing have a load weight limit? A: AS/NZS 3000:2018 does not publish numeric tray load limits. Every tray manufacturer (EzyStrut, Unistrut, Cooper B-Line, Legrand Cablofil) publishes safe working load curves based on support span — typically 25 kg/m at 3 m span for medium-duty perforated tray, up to 200 kg/m at 1.5 m span for heavy-duty ladder. The ElecAS calculator outputs cable mass per metre per tier so the responsible engineer can cross-check against the chosen tray product. Q: What reserve capacity should I use for cable tray sizing in Australia? A: Industry practice is 25–50% reserve for greenfield commercial fit-outs, 20% for tight retrofits and infrastructure, and 50–100% for mission-critical installations (data centres, hospitals, defence). The ElecAS calculator defaults to 20% but accepts any value from 0% to 100%. Set the reserve before sizing — it directly drives the recommended tray width. Q: Can I mix flat and trefoil cables on the same tray? A: Yes. The ElecAS cable tray calculator handles per-cable layout choice — three single-cores in trefoil for the heavy submain, flat-touching multicore for the lighting circuits, all on the same tier. Each cable contributes its calculated width (trefoil = 2D, flat = D, plus spacing) and the calculator packs them sequentially. Q: What tray width do I need for 4 × 25 mm² 4-core-and-earth XLPE armoured cables? A: Four touching SWA armoured 4C+E XLPE 25 mm² Cu multicores at ~28.3 mm outer diameter each require approximately 113 mm raw width. With 20% reserve that becomes 136 mm, recommending a 150 mm wide tray. Four unarmoured equivalents at ~23 mm OD would need 92 mm raw, 110 mm with reserve, fitting on a 150 mm tray as well — but a 100 mm tray would also work if the reserve is dropped to 8%. Q: Does the ElecAS calculator support ladder, perforated and solid-bottom trays? A: The calculator outputs tray width nominal which applies to ladder, perforated and solid-bottom trays — the geometric fill is the same. Depth, ventilation and current-rating implications differ between tray types (solid-bottom trays have reduced AS/NZS 3008.1.1 current ratings relative to perforated and ladder). The responsible engineer should confirm the chosen tray type against AS/NZS 3008.1.1 installation method tables. Q: Is this cable tray sizing calculator free? A: Yes. The full cable tray sizing calculator is free to use online with no sign-up required. Branded PDF reports with company logo, designer name and accent colour are included in the free tier. Cloud project sync and team workspaces are paid Pro / Team features. ## Earthing Cable Size Calculator URL: https://elecas.com.au/calculator/earth-cable-size Determine minimum protective earthing conductor sizes using AS/NZS 3000 Table 5.1 criteria. Who it is for: Designers checking protective earthing conductor sizing against active conductor and device conditions. Standards: AS/NZS 3000 Table 5.1 Key capabilities: - Look up protective earthing conductor sizes from active conductor data. - Use the result during final circuit design and compliance review. - Connect earthing outcomes with cable sizing and demand calculations. How to use: How to size an earth conductor under AS/NZS 3000:2018 1. Enter the active conductor cross-sectional area — Enter the active conductor size in mm². The calculator applies Table 5.1 to give the minimum regulatory earth size. 2. Pick the active and earth conductor material — Choose copper or aluminium for the active and the earth. The k-factor used in the Appendix B adiabatic check depends on the material combination. 3. Enter the prospective short-circuit current and clearing time — Enter the prospective short-circuit current at the protective device in kA and the device clearing time in seconds. These drive the adiabatic check. 4. Pick the insulation type — V-90 PVC (k=115 for Cu, 76 for Al), X-90 XLPE (k=143 for Cu, 94 for Al) or high-temperature insulation. The k-factor enters the adiabatic formula. 5. Review the governing result — The calculator displays both the Table 5.1 minimum and the Appendix B adiabatic result, and selects the larger as governing. Export the branded PDF citing both clauses. ### Earth cable sizing under AS/NZS 3000:2018 Table 5.1 #### What AS/NZS 3000 Table 5.1 specifies AS/NZS 3000:2018 Table 5.1 specifies the minimum earth conductor cross-sectional area as a function of the active conductor cross-sectional area for circuits where the earthing conductor is run in the same enclosure or cable as the actives. For active conductors up to 16 mm² the earth conductor must equal the active size; from 16 mm² to 35 mm² the earth must be at least 16 mm²; above 35 mm² the earth must be at least half the active size. Table 5.1 is the regulatory minimum for residual current device and overcurrent device fault loop performance. It does not account for adiabatic-equivalent sizing under high-prospective-fault-current conditions — for that, AS/NZS 3000 Appendix B Clause B6 provides the adiabatic calculation method. #### When Appendix B adiabatic sizing supersedes Table 5.1 If the prospective short-circuit current at the protective device is high and the device clearing time is slow (e.g., upstream MCCB with thermal-only protection clearing in 5 seconds), the Table 5.1 minimum earth size may be insufficient to dissipate the I²t energy without melting the insulation. The Appendix B Clause B6 adiabatic formula gives Smin = √(I²t) / k where I is the prospective fault current, t is the device clearing time and k is the insulation k-factor (115 for PVC / copper, 143 for XLPE / copper). The ElecAS earth cable sizing calculator applies both Table 5.1 and the Appendix B adiabatic calculation and reports the governing result. For most LV installations with fast-clearing MCBs the Table 5.1 minimum dominates; for slow-clearing MCCB-protected submains the adiabatic result frequently governs. #### Aluminium and parallel earth conductors Where the active conductor is aluminium, AS/NZS 3000 Table 5.1 applies as for copper but the earth-conductor material is typically still copper for thermal reasons. The k-factor for aluminium / PVC is lower (76) and the adiabatic-sized earth in aluminium would be substantially larger than the copper equivalent. Parallel installations require either (a) a single earth conductor sized for the total fault current per Table 5.1 referenced to the largest single active size, or (b) one earth conductor per parallel run, each sized per Table 5.1 referenced to the individual active size. The ElecAS calculator supports both approaches and flags the AS/NZS 3000 Clause 5.3.3.1.1 requirement. ### Frequently asked questions Q: How is the protective earthing conductor size determined? A: AS/NZS 3000:2018 Table 5.1 gives the minimum protective earthing conductor cross-sectional area as a function of the active conductor size. Larger active conductors require larger earthing conductors, with a minimum of 2.5 mm² for installations with mechanical protection. Q: Can the earthing conductor be smaller than the active? A: Yes, for active conductors above 35 mm² Table 5.1 allows the earthing conductor to be one size smaller, provided the prospective earth fault current and protective device disconnection time still satisfy the adiabatic equation in Clause 5.3.3. Q: Does the earthing conductor need to be the same material as the active? A: Not necessarily. AS/NZS 3000 Table 5.1 has separate columns for copper and aluminium. When mixing materials, apply the equivalent cross-section conversion. Q: What size earth cable do I need for a 25 mm² active under AS/NZS 3000? A: AS/NZS 3000 Table 5.1 requires the earth to be at least 16 mm² for active conductors between 16 and 35 mm² inclusive. Always also run the Appendix B Clause B6 adiabatic check against the prospective short-circuit current and device clearing time — for slow-clearing MCCB-protected submains the adiabatic result may govern with a larger earth. Q: When does the Appendix B adiabatic check govern over Table 5.1? A: When the prospective short-circuit current is high and the protective device clearing time is slow (typically thermal-only MCCB protection clearing in 1–5 seconds). For fast-clearing MCBs (≤100 ms) the Table 5.1 minimum almost always governs. Q: Can the earth conductor be smaller than the neutral in a TN-C-S installation? A: AS/NZS 3000 Table 5.1 sizes the earth (PE) conductor independently of the neutral (N) conductor. The neutral is sized for load current carrying capacity; the earth is sized for fault clearing. In a TN-C-S system the combined PEN conductor must satisfy both — typically the larger of the two governs. ## Electrical Unit Converter URL: https://elecas.com.au/calculator/converter Convert amps, kilowatts and kVA for common 1-phase and 3-phase electrical calculations. Who it is for: Users needing quick engineering conversions during load, supply and equipment calculations. Standards: General electrical engineering calculations Key capabilities: - Convert between amps, kW and kVA for common electrical design tasks. - Support quick checks during quoting, design review and commissioning. - Use as a lightweight companion to the larger ElecAS calculators. How to use: How to use the ElecAS electrical unit converter 1. Pick the conversion category — Choose power (kW / kVA / kVAr), voltage (line-line / line-neutral), current (single-phase from three-phase), or cable size (mm² / AWG). 2. Enter the input value and power factor (for power conversions) — Enter the source quantity and, for power conversions, the power factor. The calculator runs the conversion bidirectionally. 3. Read the converted result — The result includes the converted value and (for cable conversions) the nearest standard size in both metric and imperial systems. ### Electrical unit conversions for Australian electrical design #### kW, kVA and kVAr — the power triangle Real power kW, apparent power kVA and reactive power kVAr form a right triangle: kVA² = kW² + kVAr². Power factor cosφ is the ratio kW / kVA. For a 100 kW load at cosφ = 0.85, the apparent power is 117.6 kVA and the reactive power is 62.0 kVAr. Australian electrical tariffs are typically charged on apparent power (kVA demand) so reducing reactive power via PFC reduces the billed demand even though the real power is unchanged. The ElecAS converter handles all three quantities with bidirectional conversion. #### Three-phase line / phase voltage and current For a balanced three-phase circuit, line-to-line voltage = √3 × line-to-neutral voltage. The 400 V Australian distribution voltage is line-to-line; the corresponding line-to-neutral voltage is 230 V. Line current equals phase current for a star (wye) connection; for a delta connection, line current = √3 × phase current. Single-phase current from three-phase kW: I = P / (√3 × VL × cosφ) where VL is the line-to-line voltage. For 100 kW at 400 V three-phase, cosφ = 0.95: I = 100,000 / (1.732 × 400 × 0.95) = 152 A per phase. #### Cable size conversions — mm² to AWG and back Australian cable sizes are specified in mm² of conductor cross-sectional area; US National Electrical Code (NEC) uses American Wire Gauge (AWG) for smaller conductors and circular mil (kcmil) for larger. The conversion is approximate because the AWG step is not metric. 16 mm² ≈ 6 AWG; 25 mm² ≈ 4 AWG; 50 mm² ≈ 1/0 AWG; 95 mm² ≈ 4/0 AWG. For exact equivalents always go via cross-sectional area in mm², not AWG step number. The ElecAS converter reports both the exact mm² and the nearest AWG. ### Frequently asked questions Q: How do I convert kW to amps in three-phase? A: For three-phase: I (A) = (kW × 1000) ÷ (√3 × VLL × power factor). For 400 V three-phase at unity power factor, 1 kW ≈ 1.44 A. Q: How do I convert kVA to kW? A: kW = kVA × power factor. A 100 kVA load at 0.9 power factor delivers 90 kW of real power and 43.6 kvar of reactive power. Q: What is the difference between kW, kVA and kvar? A: kW is real power consumed by the load, kVA is apparent power drawn from the supply, and kvar is reactive power that circulates between source and load. They form a right triangle: kVA² = kW² + kvar². Q: How do I convert kW to kVA? A: kVA = kW / cosφ where cosφ is the power factor. For a 100 kW load at cosφ = 0.85, kVA = 100 / 0.85 = 117.6 kVA. The Australian three-phase formula I = kVA × 1000 / (√3 × VL) then gives the line current. Q: What is the line-to-neutral voltage in Australia? A: Australia uses 230 V line-to-neutral, 400 V line-to-line in the three-phase distribution system (50 Hz). The relationship is VL = √3 × VLN. Some older installations and tariff documents reference 240 V / 415 V — the actual voltage at the point of supply is typically within +10% / −6% of nominal per AS 60038. Q: What AWG is closest to 25 mm²? A: 25 mm² is closest to 4 AWG (21.15 mm²) on the smaller side and 3 AWG (26.67 mm²) on the larger side. For an exact equivalent always specify in mm² of cross-sectional area; AWG to mm² conversion is approximate because the AWG step ratio is not metric. ## Power Factor Correction Calculator — kVAR Capacitor Bank Sizing for Australia URL: https://elecas.com.au/calculator/pfc Free, browser-based power factor correction (PFC) calculator built for Australian electrical engineers, designers, electricians and estimators. Enter the real power load in kW, the existing power factor and a target power factor, and the calculator returns the required capacitive reactive power Qc = kW × (tanφ₁ − tanφ₂) in kVAR, rounds it up to the next standard capacitor bank size, and works the result through the full power triangle — initial and target apparent power (kVA), reactive power (kVAR) and the kVA demand reduction. It also sizes the delta-connected bank itself: per-phase capacitance in microfarads from C = Qc / (3·V²·ω), the nominal bank current Ic, and the ×1.5 design current that allows for capacitor tolerance, sustained overvoltage and harmonic loading. From that design current it auto-sizes a compliant bank feeder cable and circuit breaker to AS/NZS 3008.1.1:2025 (copper, X-90 XLPE, unenclosed spaced from surface, 20 m run, 2.5% voltage drop) and draws a single-line connection diagram of a packaged PFC panel with an integral regulator tapping the main switchboard busbar through its own CB and CT. Supports single-phase and three-phase systems, any nominal voltage and 50 or 60 Hz, with a branded PDF report including the power triangle and a clause-by-clause calculation breakdown. Who it is for: Electrical engineers, designers, electricians, estimators and facilities managers sizing fixed and automatic capacitor banks to improve power factor, reduce kVA demand charges and free up consumer mains capacity on commercial and industrial installations across Australia and New Zealand. Standards: AS/NZS 3000:2018 (Wiring Rules — power factor correction equipment and switchboard connection); AS/NZS 3008.1.1:2025 (Cable Selection — used to size the capacitor bank feeder cable and protective device); AS 60038 (Standard Voltages — 230 V / 400 V nominal envelope); IEC 60831 (Shunt power capacitors — tolerance and overvoltage basis for the ×1.5 design current uplift) Key capabilities: - Calculates the required capacitive reactive power Qc = kW × (tanφ₁ − tanφ₂) in kVAR to move from an existing power factor to a target power factor. - Rounds the required kVAR up to the next standard capacitor bank size from the common 1 – 600 kVAR ladder so the recommendation matches real switchable bank steps. - Sizes the delta-connected bank — per-phase capacitance in microfarads from C = Qc / (3·V²·2πf), the nominal bank current Ic, and the ×1.5 design current that covers capacitor tolerance, overvoltage and harmonic loading. - Auto-sizes a compliant bank feeder cable and circuit breaker on the ×1.5 design current to AS/NZS 3008.1.1:2025 (copper, X-90 XLPE, unenclosed spaced from surface, 20 m, 2.5% voltage drop) — a one-click estimate that hands off to the full Cable Selection tool for fault and earth-loop checks. - Draws a power triangle showing initial apparent power (S1), target apparent power (S2), both reactive components and the correction Qc, plus the kVA demand reduction and the line-current reduction percentage at the same active power. - Generates a single-line connection diagram of a packaged PFC panel with an integral PF controller/regulator, contactor and delta capacitor bank tapping the MSB busbar through its own CB and incomer CT. - Works for single-phase and three-phase systems at any nominal voltage and 50 or 60 Hz, and exports a branded PDF report with the power triangle and a step-by-step calculation breakdown. How to use: How to size a power factor correction capacitor bank 1. Enter the real power load in kW — Enter the connected real power load in kilowatts. For a mixed load use the operating-time-weighted average real power from a kWh meter or measurement. 2. Set the current power factor — Drag the Current Power Factor slider to the measured existing power factor (cosφ), typically read from a power-quality meter or the utility bill. The slider covers 0.50 to 0.99. 3. Set the target power factor — Drag the Target Power Factor slider to the value you want to reach — usually 0.90 or 0.95 to clear a network power factor penalty. The target cannot be set below the current power factor. 4. Enter the system voltage and frequency — Enter the nominal line voltage (for example 400 V three-phase or 230 V single-phase) and the supply frequency (50 Hz in Australia, 60 Hz elsewhere). These drive the delta capacitance and bank current. 5. Read the required kVAR and standard bank size — The calculator shows the required correction Qc = kW × (tanφ₁ − tanφ₂) in kVAR and rounds it up to the next standard bank size, alongside the per-phase delta capacitance in µF, the nominal bank current Ic and the ×1.5 design current. 6. Check the auto-sized bank cable and export the PDF — Review the automatically sized AS/NZS 3008.1.1 bank feeder cable and breaker on the connection diagram, then export the branded PDF report with the power triangle and the full calculation breakdown. ### Power factor correction capacitor bank sizing for Australian installations #### Why power factor correction matters A low power factor (cosφ below 0.90) means the installation draws more apparent power (kVA) than real power (kW), increasing the current in the consumer mains, the I²R losses, the voltage drop and the kVA capacity charged by the network operator. Most Australian distribution network tariffs apply a kVA demand charge or a power factor penalty when the monthly average drops below 0.90; some commercial tariffs require 0.95. Power factor correction adds capacitive reactive power (kVAR) to offset the inductive kVAR drawn by motors, transformers and other reactive loads, bringing cosφ closer to unity. Correctly sized PFC reduces the kVA demand and the line current for the same real power output, and on most commercial sites pays for itself in 6–24 months. #### The PFC sizing formula The required capacitive reactive power is Qc = P × (tanφ₁ − tanφ₂) where P is the real power in kW, φ₁ is the original power factor angle and φ₂ is the target. For P = 100 kW, original cosφ = 0.75 (tanφ = 0.882), target cosφ = 0.95 (tanφ = 0.329), Qc = 100 × (0.882 − 0.329) = 55.3 kVAR. The ElecAS calculator works this through the full power triangle. It reports the initial apparent power S1 = kW / cosφ₁ and reactive power Q1 = kW × tanφ₁, the target apparent power S2 = kW / cosφ₂ and reactive power Q2, the correction Qc = Q1 − Q2, and the resulting kVA demand reduction (S1 − S2) and line-current reduction percentage. The required kVAR is then rounded up to the next standard capacitor bank size from the common ladder (1, 2.5, 5, 7.5, 10 … 600 kVAR) so the recommendation matches a real switchable bank. #### Delta capacitance, bank current and the design-current uplift For a delta-connected bank the per-phase capacitance is C = Qc / (3 × V² × ω) where V is the line voltage and ω = 2πf. The calculator reports this in microfarads (µF) so the bank can be specified or checked against a manufacturer step rating. It also computes the nominal bank current Ic = (kVAR × 1000) / (√3 × V) from the installed standard bank size. A capacitor bank draws more than its nominal current in service: IEC 60831 permits up to +10% capacitance tolerance and sustained overvoltage of about 10%, and harmonic currents add further loading. ElecAS therefore applies a ×1.5 uplift to Ic to give a design current, and sizes the bank feeder cable and circuit breaker on that figure — the standard approach for protecting and connecting a capacitor bank. #### Automatic bank cable and breaker sizing to AS/NZS 3008.1.1 From the ×1.5 design current the calculator auto-sizes a compliant bank feeder cable and protective device to AS/NZS 3008.1.1:2025 using a fixed reference install — copper conductor, X-90 XLPE insulation, unenclosed and spaced from the surface, a 20 m run and a 2.5% maximum voltage drop. The result names the cable (for example 4C 16 mm² Cu XLPE (X-90) + earth) and the matching breaker rating. This inline estimate is intended for early sizing. For a project-specific result that accounts for the real installation method, grouping and ambient derating, the prospective fault level, the adiabatic short-circuit withstand check and the earth-fault loop impedance, hand the design off to the full ElecAS Cable Selection calculator. #### Connecting the bank — packaged PFC panel For network-charge correction the bank is connected at the main switchboard. The single-line diagram on the page shows a packaged PFC panel — supplied complete with an integral PF controller/regulator, contactor and delta-connected capacitor bank — tapping the MSB busbar through its own circuit breaker and feeder cable, with the incomer current transformer (CT) signal feeding the regulator so the bank switches to suit the measured load. Where the load profile varies (commercial offices, retail, mixed industrial), an automatic stepped bank switches capacitor stages on and off as the load changes to avoid leading power factor at light load. Where significant harmonic-generating load exists (variable-frequency drives, large rectifiers), detuned banks add a series reactor tuned away from the dominant harmonic, and harmonic-filtered banks add tuned filters, to prevent resonance and capacitor failure. ### Frequently asked questions Q: How is capacitor bank size calculated for power factor correction? A: The required capacitive reactive power is Qc = kW × (tanφ₁ − tanφ₂), where φ₁ is the existing power factor angle and φ₂ is the target. For a 100 kW load improving from 0.75 PF (tanφ = 0.882) to 0.95 PF (tanφ = 0.329), Qc = 100 × (0.882 − 0.329) ≈ 55 kVAR. The ElecAS calculator then rounds this up to the next standard bank size. Q: What target power factor should I aim for in Australia? A: Most Australian distribution network tariffs apply a kVA demand charge or a power factor penalty below 0.90, and some commercial tariffs target 0.95. A practical target is 0.95 lagging — high enough to clear most penalties without over-correcting. Correcting close to unity or into leading power factor at light load can cause overvoltage and resonance, so the calculator caps the target at the existing power factor as a floor. Q: Where should the capacitor bank be installed? A: To reduce network demand charges, install at the main switchboard (global correction) — this is the packaged PFC panel shown in the connection diagram, tapping the MSB busbar through its own CB and CT. To also cut internal cable losses and free up upstream capacity, install close to large inductive loads such as motors and transformers (local correction). Where significant harmonic-generating load exists (VFDs, large rectifiers), use detuned or harmonic-filtered banks to avoid resonance. Q: Why does the bank cable and breaker use a ×1.5 design current? A: A capacitor bank draws more than its nominal current Ic in service: IEC 60831 allows capacitance up to +10% tolerance, sustained overvoltage up to ~10%, and harmonic currents add further loading. Standard practice is to size the bank feeder cable and protective device at about 1.5 × the nominal bank current. ElecAS computes Ic from the installed standard bank size, applies the ×1.5 uplift, and sizes the cable and CB on that design current to AS/NZS 3008.1.1. Q: How much will power factor correction reduce my demand? A: Correcting power factor reduces apparent power (kVA) and line current for the same real power (kW). Moving 100 kW from 0.75 to 0.95 PF drops apparent power from 133.3 kVA to 105.3 kVA — a 21% reduction in kVA demand and line current. The ElecAS calculator shows the initial and target kVA, the kVA reduction and the line-current reduction percentage directly from the power triangle. Q: How do I calculate the required kVAR for power factor correction? A: Qc = P × (tanφ₁ − tanφ₂) where P is the real power in kW, φ₁ is the original power factor angle and φ₂ is the target power factor angle. For a 100 kW load at cosφ = 0.75 corrected to cosφ = 0.95, Qc = 100 × (0.882 − 0.329) = 55.3 kVAR. The ElecAS calculator then rounds this up to the next standard capacitor bank size. Q: How do I find the capacitance in microfarads for a power factor correction bank? A: For a delta-connected bank the per-phase capacitance is C = Qc / (3 × V² × 2πf), where Qc is the correction in VAR, V is the line voltage and f is the frequency. The ElecAS calculator reports this value in microfarads (µF) directly, so you can specify or check the capacitor step against a manufacturer rating. Q: What size cable and breaker does a capacitor bank need? A: Size them on the bank design current, not the nominal current. The nominal bank current is Ic = (kVAR × 1000) / (√3 × V); standard practice uplifts this by about 1.5× to allow for the IEC 60831 capacitance tolerance, sustained overvoltage and harmonic loading. ElecAS applies the ×1.5 uplift and auto-sizes a compliant cable and breaker to AS/NZS 3008.1.1:2025 from that design current. Q: How much does power factor correction reduce demand and current? A: Correcting power factor lowers the apparent power (kVA) and the line current for the same real power (kW). Moving 100 kW from 0.75 to 0.95 PF reduces apparent power from 133.3 kVA to 105.3 kVA — about a 21% reduction in kVA demand and line current. The ElecAS calculator shows the initial and target kVA, the kVA reduction and the line-current reduction percentage. Q: Can over-correction cause problems? A: Yes. Over-correction at light load produces a leading power factor which can cause voltage rise, damage motors and trip generator-set protective relays. Avoid it by sizing the bank to a realistic target (around 0.95) rather than unity, and by using an automatic stepped bank that switches capacitor stages on and off as the load varies. Q: Where should a power factor correction bank be installed? A: To reduce network demand charges, install at the main switchboard (global correction) — the packaged PFC panel shown in the connection diagram, tapping the MSB busbar through its own CB and CT. To also cut internal cable losses and free up upstream capacity, install close to large inductive loads such as motors and transformers (local correction). ## Generator Sizing Calculator URL: https://elecas.com.au/calculator/generator-sizing Size a diesel or gas generator from connected load, motor starting scenarios and duty class — recommended kVA from the standard alternator ladder, plus fuel tank volume for any required autonomy. Who it is for: Electrical engineers, designers, contractors and facilities managers specifying standby, prime or continuous diesel and gas generator sets for Australian and New Zealand installations. Standards: AS ISO 8528.1; AS ISO 8528.5; AS/NZS 3000:2018; AS/NZS 3010:2017; AS 60038 Key capabilities: - Choose Prime (PRP), Standby (ESP) or Continuous (COP) duty to AS ISO 8528.1 with manufacturer max-loading defaults (70 / 80 / 100%) — override per project. - Model motor starting with DOL (7.5×), Star-Delta (2.5×), Soft Starter (3.5×) and VFD (1.2×) factors; worst-case starting scenario governs the sizing automatically. - Add an unlimited list of motors with rated kW, quantity and start method — the calculator starts the largest while all others run. - Size the fuel day tank for any autonomy with manufacturer consumption data or an auto-estimate (~0.22 L/hr per kVA at load), including a safety reserve. - Recommended nameplate kVA selected from the standard alternator ladder (10 – 3000 kVA), plus full-load current for 1Ø 230 V or 3Ø 415 V systems. - Export a branded PDF report with project details, load breakdown, motor schedule and fuel tank sizing — ready to drop into a design submission. How to use: How to size a generator for an Australian installation 1. List the connected loads — Enter each load as kW + power factor + start type (DOL, soft-starter, VFD, static). Distinguish always-on loads from intermittent loads. 2. Run the steady-state kW and kVA checks — The calculator sums the connected kW and kVA and reports the steady-state requirement, with diversity applied via AS/NZS 3000 Appendix C for the always-on portion. 3. Identify the largest motor or block-load step — The calculator picks the largest single load step (typically the largest DOL motor) and computes the starting kVA and starting power factor. 4. Apply the transient voltage and frequency dip checks — Enter the maximum acceptable voltage dip (typically 15% for normal services, 10% for medical) and frequency dip (typically 10%). The calculator picks the smallest alternator that meets the dip limits. 5. Review the four-check result and pick the rating — The calculator reports the kW required by each check and picks the governing rating. Choose standby, prime or continuous as appropriate. Export the branded PDF. ### Generator sizing for Australian standby and prime power installations #### The four generator sizing checks A diesel or gas generator must satisfy four independent sizing checks: steady-state kW (real power continuous load), steady-state kVA (apparent power continuous load + load step capacity), transient voltage dip (the voltage sag during the largest motor start), and transient frequency dip (the frequency sag during the largest motor start or block-load step). The largest of the four governs the generator nameplate rating. AS 3010 and AS 60034 govern the engineering for generating sets in Australian installations. Manufacturer transient performance curves (typically published for 10%, 25% and 50% load steps) determine the transient checks. #### Motor-start governs most building services generators A 22 kW direct-on-line motor draws 6–8× full-load current at start (200–250 A on a 400 V three-phase mains) at a starting power factor near 0.35 lagging. The kVA draw during start is therefore 80–100 kVAr inrush, which can dip the generator voltage by 15–25% depending on the alternator subtransient reactance. For most building services applications (life-safety pumps, lift, smoke-exhaust fans, kitchen exhaust) the largest motor start is the governing sizing check. Reduced-voltage starting (soft starter, VFD, star-delta) cuts the starting kVA by 50–70% and is often the most economical way to reduce the generator size. #### Standby vs prime vs continuous ratings Standby (ESP) rating is for emergency standby use only — typically rated for 200 hours per year at 70% average load with no overload capability. Prime (PRP) rating is for primary power supply with utility unavailable — rated for unlimited hours at 70% average load with 10% overload for 1 hour in 12. Continuous (COP) rating is for unlimited hours at 100% load with no overload. Most Australian building services applications use the standby rating. Off-grid mining or remote prime power applications use PRP. The ElecAS generator sizing calculator reports the required nameplate at all three rating bases. ### Frequently asked questions Q: What is the difference between Prime, Standby and Continuous generator ratings? A: AS ISO 8528.1 defines Emergency Standby Power (ESP) for utility-outage backup with no overload and limited annual hours; Prime Power (PRP) for variable loads with unlimited hours but a ~70% average load cap; and Continuous Operating Power (COP) for constant base loads at 100% of nameplate for unlimited hours. The calculator applies 80% / 70% / 100% max-loading defaults to the respective duties. Q: Why is a generator typically not loaded beyond 80%? A: Manufacturers such as Cummins (T-030) and Caterpillar (LEBW4977) recommend keeping standby generators at or below about 80% of nameplate for a margin against transient loads, starting kVA and engine health. Prime-rated sets target ~70% average load per ISO 8528.1 PRP, while continuous sets can run at 100%. Q: How is the recommended generator kVA calculated? A: Running kVA = connected kW ÷ power factor, plus the motors running kVA. For each motor the worst-case starting scenario is evaluated: largest motor starting while all other motors (including remaining units of the same type) run at full load. The sizing target is max(Running, Starting) ÷ max-loading %, rounded up to the next standard alternator size (10, 15, 20, … 3000 kVA). Q: How do I include motor starting in generator sizing? A: Enable the Motor Starting section and add each motor with its rated kW, quantity and start method. The calculator applies the AS/IEC starting kVA factor for Direct-On-Line (7.5×), Star-Delta (2.5×), Soft Starter (3.5×) or VFD/VSD (1.2×), then checks the worst-case starting scenario against the running load. Whichever is larger governs the recommended kVA. For transient voltage dip limits refer to AS ISO 8528.5. Q: What starting kVA multiplier should I use for DOL, Star-Delta, Soft Starter and VFD? A: Typical locked-rotor / transient factors used for generator sizing are: Direct-On-Line 6–8× rated kW (default 7.5×), Star-Delta 2–3× (default 2.5×), Soft Starter 3–4× (default 3.5×) and VFD/VSD 1.0–1.5× (default 1.2×). Confirm against motor and drive data sheets — actual values depend on motor design class and soft-starter / VFD current limit settings. Q: How do I size the diesel fuel tank for a generator? A: Required fuel volume = consumption (L/hr) × autonomy (hours) × (1 + reserve %). If a manufacturer consumption figure is not available, the calculator estimates from the recommended kVA at the chosen loading (~0.22 L/hr per kVA for modern diesel gensets). Include a 10–20% reserve to cover unusable bottom-of-tank volume, filtration margin and refuelling buffer. Day tanks, bulk tanks and bunded installations must also meet AS 1940 and local environmental requirements. Q: What is the typical diesel generator fuel consumption per kVA? A: Modern diesel gen-sets consume roughly 0.20–0.25 L/hr per kVA at typical load factors, with a common design figure of 0.22 L/hr/kVA. Consumption scales approximately with load — a 500 kVA set at 80% load burns about 500 × 0.8 × 0.22 ≈ 88 L/hr. Always confirm with the manufacturer fuel consumption curve when available. Q: How many hours of autonomy should a standby generator have? A: Typical design autonomies are 8–12 hours for a belly tank, 24 hours for essential-services standby (hospitals, data centres), and 48–72 hours or more for remote sites and critical life-safety installations. Local authority, insurance and AS/NZS 3009 / essential-services requirements may dictate minimum fuel reserves. Q: Does the calculator handle single-phase and three-phase systems? A: Yes. Select 1-Phase (typically 230 V) or 3-Phase (typically 415 V); the full-load current is computed with the correct phase factor (I = kVA × 1000 ÷ V for single-phase, and I = kVA × 1000 ÷ (√3 × V) for three-phase) per AS 60038 nominal voltages. Q: Which Australian Standards apply to generator set installations? A: AS ISO 8528.1 defines duty ratings and application of reciprocating IC engine driven AC generating sets. AS ISO 8528.5 covers transient voltage and frequency performance on motor starting. AS/NZS 3010:2017 sets out installation, earthing, neutral switching and changeover requirements. AS/NZS 3000:2018 (Wiring Rules) applies to the downstream installation. AS 1940 governs fuel storage. Q: How do I size a generator for a building services standby application? A: Run the four-check sizing: steady-state kW (continuous load with AS/NZS 3000 Appendix C diversity), steady-state kVA (continuous apparent power), transient voltage dip (during the largest motor start), and transient frequency dip (during the largest block load step). Pick the rating that satisfies the largest of the four checks at the standby (ESP) rating basis. Q: What is the difference between standby (ESP), prime (PRP) and continuous (COP) generator ratings? A: Standby (ESP) is for emergency use only — typically 200 hours/year at 70% average load with no overload. Prime (PRP) is for unlimited hours of primary power at 70% average load with 10% overload for 1 hour in 12. Continuous (COP) is for unlimited hours at 100% load with no overload. Q: How much does soft-starting a motor reduce generator size? A: A soft-starter typically reduces starting current to 2–3× full-load current (vs 6–8× for DOL), cutting the starting kVA by 50–70%. For building services applications where the largest motor start governs the generator sizing, soft-starting often allows a 30–50% smaller generator. Q: Should I include AS/NZS 3000 Appendix C diversity in generator sizing? A: Yes for the steady-state continuous load — the same Appendix C diversity factors apply. Do not apply diversity to the largest single motor for the transient voltage / frequency dip check, because the start of that single motor is a single event regardless of overall load diversity. ## UPS & Battery Sizing Calculator URL: https://elecas.com.au/calculator/ups-battery Size a UPS battery bank from critical load (kW), backup time and DC bus voltage — returns required Ah, blocks per string, parallel strings, total capacity, achieved autonomy and indicative weight / footprint. Who it is for: Electrical engineers, critical-power designers, data-centre engineers, contractors and specifiers sizing UPS battery banks for Australian and New Zealand installations. Standards: IEEE 485; IEEE 1184; IEEE 1189; AS 62040; AS/NZS 3000:2018 Key capabilities: - IEEE 485 / 1184 / 1189 constant-current sizing with aging factor (1.25 default for 80% end-of-life capacity), temperature derating and engineering design margin. - Supports VRLA (sealed lead-acid), LiFePO4 (lithium iron phosphate), Li-Ion (NMC / NCA) and Ni-Cd (vented) chemistries with preset nominal and end-of-discharge voltages. - Phase-aware DC bus voltage selector (48 / 96 / 120 / 192 / 240 V single-phase, 240 / 384 / 480 V three-phase) with plain-English guidance for each option. - Solves blocks in series per string, parallel strings, total installed Ah / kWh and the autonomy the bank actually delivers at the design load. - Indicative bank weight, volume and floor footprint per chemistry for early layout and plant-room planning. - Export a branded PDF report with project details, hero result card, system parameters, sizing breakdown, battery bank configuration, warnings and method & standards references. How to use: How to size a UPS battery using IEEE 485 / 1184 / 1189 1. Define the discharge profile — Enter each load segment of the discharge profile as (current in A, duration in minutes). The profile can be a flat constant load or a stepped profile (e.g., 30 s inrush, 5 min full load, 25 min reduced load). 2. Pick the battery chemistry — Choose VLA (IEEE 485), VRLA (IEEE 1184), Ni-Cd (IEEE 1189), LiFePO4 or Li-Ion. The calculator applies the corresponding sizing method and chemistry limits. 3. Set the temperature, aging and design margins — Enter the design ambient temperature (typically 25 °C for battery rooms; higher for outdoor cabinets), the aging margin (1.25 for 80% end-of-life standard, 1.15 for shorter-life applications) and the design margin (typically 1.10). 4. Set the end-of-discharge voltage and depth-of-discharge limit — For lead-acid the end-voltage is typically 1.75–1.80 V/cell. For lithium the depth-of-discharge limit (80% LiFePO4, 90% Li-Ion) caps usable capacity. 5. Review the governing section and required Ah — The calculator displays the per-section capacity requirement, identifies the governing section and reports the required Ah at the specified discharge rate. Export the branded PDF citing IEEE 485 / 1184 / 1189. ### UPS battery sizing — IEEE 485, IEEE 1184 and IEEE 1189 in practice #### The three sizing standards IEEE 485 (vented lead-acid VLA) is the original constant-current sizing standard widely used for stationary UPS, switchgear DC and substation battery installations. IEEE 1184 covers valve-regulated lead-acid (VRLA) and adapts the 485 method with VRLA-specific aging and float-correction factors. IEEE 1189 covers nickel-cadmium (Ni-Cd) sizing for high-reliability installations. The ElecAS UPS battery calculator implements all three and adds lithium-ion (LiFePO4 and Li-Ion) sizing using the manufacturer recommended depth-of-discharge and C-rate limits. The calculation produces the required Ah capacity at the specified discharge rate and runtime. #### The constant-current sizing method For each load segment of the discharge profile, the required capacity is C = (I × K) / (kt × kc × kτ × kd) where I is the segment current, K is the manufacturer time-correction factor, kt is the temperature correction, kc is the design margin, kτ is the aging margin (typically 1.25 for 80% end-of-life) and kd is the depth-of-discharge limit for the chemistry. The total required capacity is the larger of the cumulative section requirements across the discharge profile. The calculator runs the full IEEE 485 / 1184 / 1189 section iteration and reports the governing section. #### Lithium chemistry sizing differences LiFePO4 and Li-Ion batteries follow a different sizing approach because the cell voltage stays high throughout the discharge curve and the published Ah rating is closer to the usable Ah. The depth-of-discharge limit (typically 80% for LiFePO4, 90% for Li-Ion) and the C-rate limit (typically 1C continuous for LiFePO4, 2C for Li-Ion) govern the sizing. The ElecAS calculator applies the chemistry-specific limits and accounts for the typically longer cycle life of lithium (3000–6000 cycles at 80% DoD vs 500–1500 for VRLA). The total cost of ownership comparison built into the report often favours lithium for installations with frequent partial discharge. ### Frequently asked questions Q: How do I size a UPS battery bank? A: Start with the critical load (kW), required backup time (minutes), UPS inverter efficiency and DC bus voltage. Convert to DC load current (P_dc = kW ÷ efficiency, I_dc = P_dc ÷ V_dc), multiply by backup hours to get raw Ah, then apply aging factor (typ. 1.25), temperature derating and design margin. Blocks per string = ⌈V_dc ÷ V_unit⌉ and parallel strings = ⌈Required Ah ÷ Block Ah⌉ — this is the IEEE 485 / 1184 constant-current approximation the calculator uses. Q: What is the IEEE 485 aging factor and why is it 1.25? A: IEEE 485 requires oversizing the battery so it still meets the load at end-of-life, commonly defined as 80% of rated capacity (1 ÷ 0.8 = 1.25). This aging factor is applied on top of the raw Ah demand so that a battery at end-of-life still delivers the specified backup time. Lithium banks often use lower factors (1.1 – 1.2) with tighter BMS monitoring. Q: Which battery chemistry is best for a UPS — VRLA, LiFePO4, Li-Ion or Ni-Cd? A: VRLA is cheapest with 5 – 10 year life, best for short backups up to 30 minutes. LiFePO4 (lithium iron phosphate) is the most popular choice today for 10 – 15 year life, compact footprint and safe chemistry. Li-Ion (NMC / NCA) has the highest energy density but needs a certified BMS and fire-safety controls. Ni-Cd (vented) is heavy-duty, tolerates extreme temperatures and lasts 20+ years — typical for rail, switchyard and substation DC. Q: What DC bus voltage should I pick for my UPS? A: 48 V / 96 V / 120 V suit small telecom and single-phase UPS up to ~3 kVA. 192 V / 240 V are common for 5 – 20 kVA single-phase UPS. 240 V also covers entry-level 3-phase UPS ≤ 20 kVA. 384 V is the most common 3-phase UPS DC bus for 20 – 200 kVA, and 480 V is used for large data-centre and industrial 3-phase UPS. The calculator filters the DC bus options by the phase you select. Q: Why does the calculator need UPS efficiency and how does it affect battery size? A: The battery has to supply the inverter input, not the AC output. If the inverter is 94% efficient, the DC side draws 1 ÷ 0.94 ≈ 6.4% more kW than the AC load. Higher efficiency gives a smaller battery for the same autonomy. Typical online (double-conversion) UPS efficiency is 92 – 96%; confirm with the manufacturer data sheet for the selected duty point. Q: How do aging, temperature and design margin combine in the sizing? A: The calculator multiplies the raw Ah by aging × (1 + design margin %) and divides by the temperature derating factor. Aging 1.25 covers capacity fade to 80%, temperature derating < 1.0 accounts for operation below 25 °C (battery capacity falls with cold), and design margin adds engineering headroom (typ. 10 – 20%) for unmeasured losses, future load creep and commissioning tolerance. Q: Does the calculator work for single-phase (230 V) and three-phase (415 V) UPS? A: Yes. Select 1-Phase or 3-Phase; the AC load current is computed with the correct phase factor (I = kVA × 1000 ÷ V for single-phase, I = kVA × 1000 ÷ (√3 × V) for three-phase) per AS 60038 nominal voltages. The DC bus options are filtered to show only voltages typical for the selected phase. Q: What warnings does the calculator check? A: The calculator flags an end-of-discharge string voltage that is too close to the DC bus (inverter under-voltage risk), UPS efficiency below 85% (verify manufacturer data), VRLA banks sized beyond 60 minutes (consider lithium for long autonomy) and block / bus voltage mismatches where cells in series do not divide evenly into the DC bus — with a specific fix suggesting either changing the DC bus or the Unit Nominal voltage. Q: Which Australian and international standards apply to UPS battery installations? A: IEEE 485 (vented lead-acid) and IEEE 1189 (VRLA) are the reference sizing methods; IEEE 1184 is the UPS-specific sizing guide. AS 62040 covers UPS safety, EMC and performance. AS/NZS 3000:2018 (Wiring Rules) applies to the AC installation, including battery-room ventilation and segregation. AS/NZS 4777.1 and AS/NZS 5139 may also apply for renewable-integrated UPS and lithium battery installations. Q: Can the calculator export a PDF report? A: Yes. The Export PDF button generates a branded report including project details, the recommended battery bank (total Ah, cells per string, parallel strings, chemistry), system parameters, sizing breakdown with all factors, battery bank configuration, indicative weight and footprint, design-notes warnings, and a method / standards reference section. Q: Which IEEE standard applies to my UPS battery sizing? A: IEEE 485 for vented lead-acid (VLA), IEEE 1184 for valve-regulated lead-acid (VRLA), IEEE 1189 for nickel-cadmium (Ni-Cd). Lithium chemistries (LiFePO4, Li-Ion) follow manufacturer guidance with depth-of-discharge and C-rate limits — the ElecAS calculator includes lithium sizing alongside the IEEE methods. Q: What aging margin should I use for a 20-year battery? A: A typical aging margin is 1.25 (80% end-of-life capacity). Some high-reliability installations use 1.43 (70% end-of-life) for substation-grade applications. The aging margin multiplies the required capacity, so a 100 Ah profile at 1.25 aging requires a 125 Ah nameplate battery. Q: How does temperature affect battery sizing? A: Lead-acid capacity drops below 25 °C and rises above 25 °C, but cycle life drops sharply above 30 °C. Lithium cell capacity is more stable across temperature but charge / discharge current capability drops below 0 °C. The calculator applies the chemistry-specific temperature correction factor automatically. Q: Can lithium replace lead-acid in an existing UPS without resizing? A: Usually no. Lithium nameplate Ah is closer to usable Ah than lead-acid nameplate Ah, so a like-for-like replacement may give more runtime than required (wasteful) or trip the UPS charger if the maximum charge current is exceeded. Always resize per the lithium chemistry sizing method. ## Solar & Battery ROI Calculator URL: https://elecas.com.au/calculator/solar-roi Estimate the return on investment of a solar PV system, a home battery, or both — payback period, NPV, IRR, total savings and ROI, with Australian feed-in tariff modelling and a cumulative cash-flow projection. Who it is for: Electrical engineers, solar designers, energy consultants, installers and homeowners evaluating the financial return of solar PV and battery storage in Australia. Standards: AS/NZS 4777; AS/NZS 5139 Key capabilities: - Three modes — Solar Only, Solar + Battery, and Battery Retrofit — each with its own self-consumption and savings model. - Returns simple payback, discounted payback, NPV, IRR, total savings and ROI percentage from a configurable discount rate and analysis horizon. - Optional advanced projection escalates electricity tariffs and fades output year-on-year, with a cumulative cash-flow chart that marks the break-even point. - Models self-consumption at the import tariff and exports at the feed-in tariff, with battery retrofit shifting spare solar from export into evening self-consumption. - Export a branded PDF report with project details, ROI summary, cost breakdown, energy assumptions and a year-by-year cash-flow table. How to use: How to calculate solar and battery ROI for an Australian installation 1. Choose the mode — Pick Solar Only, Solar + Battery or Battery Retrofit. Solar Only and Solar + Battery model a new system; Battery Retrofit values a battery added to existing solar by storing spare exported energy. 2. Set system size and location — Enter the solar size in kW and select your city. The location preset applies a realistic specific yield (kWh per kW per year) — Sydney ~1420, Melbourne ~1310, Brisbane and Adelaide ~1530, Perth and Darwin ~1600 — or choose Custom to enter your own yield. 3. Enter the installed price net of rebates — Enter the total installed cost after deducting STCs and any battery rebate such as Cheaper Home Batteries, so every result reflects the real price you pay. 4. Set your tariffs and usage — Enter your grid import rate (c/kWh), feed-in tariff (c/kWh) and daily usage (kWh). For battery modes, set usable battery capacity, round-trip efficiency and effective cycles per year. 5. Set the self-consumption share — Enter the percentage of generation you use directly. A higher self-consumption share — and a battery — shifts energy from low-value export to high-value self-use and shortens payback. 6. Choose the discount rate and horizon — Pick a discount rate (e.g. 5%) and an analysis horizon (5–30 years). Optionally set price escalation and output degradation under advanced assumptions for a rising-cost scenario. 7. Review the metrics and export the report — Read the simple and discounted payback, NPV, IRR, lifetime savings and ROI%, check the break-even point on the cumulative cash-flow chart, and export the branded PDF for the proposal or record. ### Solar & battery ROI in Australia — payback, NPV and IRR explained #### Is solar worth it in Australia in 2026? For most Australian homes and businesses a well-sized rooftop solar system still pays for itself in roughly 4 to 7 years and then delivers free electricity for the remaining 18–20+ years of its life. The return depends on three things you control and one you do not: the installed price (after STC rebates), how much of the generation you use yourself versus export, your grid import tariff and feed-in tariff, and how much sun your roof actually receives. The ElecAS Solar & Battery ROI calculator turns those inputs into the four numbers that actually decide the case — payback period, net present value (NPV), internal rate of return (IRR) and lifetime savings — instead of a single optimistic headline figure. The economics have shifted: feed-in tariffs have fallen to roughly 3–8 c/kWh in most states while grid import rates sit around 25–45 c/kWh. That gap is why self-consumption — using your own solar at the moment it is generated — is now far more valuable than exporting it, and why a correctly modelled self-consumption share matters more to your payback than the system size alone. #### How the three modes model the return Solar Only estimates annual generation as system size (kW) × specific yield (kWh per kW per year for your location), splits it into self-consumed energy valued at your import rate and exported energy valued at the feed-in tariff, and nets the result against the installed price. The location preset sets a realistic specific yield — for example about 1420 kWh/kW/yr in Sydney, 1310 in Melbourne, 1530 in Brisbane and Adelaide, and 1600 in Perth and Darwin — so the generation figure reflects real Australian and New Zealand sun rather than a nameplate ideal. Solar + Battery applies a higher self-consumption share because the battery stores midday surplus that would otherwise export cheaply and discharges it in the evening to displace expensive grid import. Battery Retrofit values each stored kilowatt-hour at (round-trip efficiency × import rate − feed-in tariff) — the true marginal benefit of shifting a unit of spare solar from export to evening use — and caps it at the spare solar actually available to store. If the feed-in tariff is high relative to the import rate, the tool flags that storing energy may save little. #### Payback, NPV and IRR — which number should you trust? Simple payback (net cost ÷ annual savings) is the most intuitive figure and the one most quoted, but it ignores the time value of money and everything that happens after break-even. NPV discounts every year of savings back to today at your chosen discount rate and subtracts the upfront cost — a positive NPV means the system beats that hurdle rate, and it captures the full system life, not just the years up to payback. IRR is the discount rate at which NPV equals zero, so you can compare it directly against a term deposit, an offset account or your cost of capital. For a household decision, payback period and lifetime savings are usually the clearest lens. For a commercial or investment decision, NPV and IRR are the defensible metrics. The ElecAS calculator reports all of them from one set of inputs, plus a cumulative cash-flow chart that marks the exact break-even point, so you can present whichever framing your audience expects. #### Is a home battery worth it yet? A battery rarely pays for itself on arbitrage alone at today’s prices, but the gap has narrowed sharply with the federal Cheaper Home Batteries program cutting upfront cost and rising import tariffs increasing the value of each stored kilowatt-hour. The honest test is the marginal one: every kWh you cycle through the battery is worth roughly your import rate minus your feed-in tariff, less round-trip losses (typically 5–15%). Multiply that by realistic daily throughput and the cycles the battery actually achieves — not its nameplate capacity — and compare the lifetime total against the installed price. Run the Battery Retrofit mode to value a battery added to an existing solar array, or Solar + Battery to model both together. Because the calculator separates the battery’s contribution, you can see exactly what the battery adds on top of solar rather than crediting it with savings the panels would have delivered anyway. #### Rebates, escalation and degradation Enter the installed price net of rebates: deduct small-scale technology certificates (STCs) and any federal or state battery incentive such as Cheaper Home Batteries before entering the figure. Keeping rebates out of the model means the payback, NPV and IRR always reflect the real price you pay, and the result does not silently go stale when a scheme changes. The optional advanced assumptions let you escalate the electricity tariff each year (electricity prices have historically risen faster than CPI) and fade output year-on-year for panel and battery degradation, so you can stress-test a level baseline against a more realistic rising-cost scenario. The output is an indicative engineering estimate, not a quote or financial advice. It is most accurate when you use your own retailer tariffs, a quoted installed price and a realistic self-consumption share for your usage pattern. Export the branded PDF report — project details, ROI summary, cost breakdown, energy assumptions and the year-by-year cash-flow table — for a client proposal or your own records. ### Frequently asked questions Q: How is solar payback calculated? A: Simple payback = net upfront cost (after STC and other rebates) ÷ annual savings. Annual savings come from self-consumed generation valued at your grid import rate, plus exported generation valued at the feed-in tariff. The calculator also reports discounted payback, which accounts for the time value of money at your chosen discount rate. Q: What is the difference between NPV and IRR for a solar investment? A: NPV (net present value) discounts every year of savings back to today’s dollars and subtracts the net upfront cost — a positive NPV means the system beats your discount rate. IRR (internal rate of return) is the discount rate at which NPV equals zero, so you can compare it directly against your cost of capital or alternative investments. Q: How does adding a battery change the return? A: A battery raises self-consumption — storing midday surplus that would otherwise export at a low feed-in tariff and discharging it in the evening to offset grid import at a much higher rate. The Solar + Battery mode applies a higher self-consumption share, and the Battery Retrofit mode values each stored kWh at (round-trip efficiency × import rate − feed-in tariff). Q: How are rebates handled? A: You enter the total installed price net of any rebates — deduct STCs (small-scale technology certificates) and any federal or state battery incentives such as Cheaper Home Batteries yourself before entering the figure. Because those schemes change frequently and vary by state, keeping them out of the model means the payback, NPV and IRR always reflect the real price you pay. Q: Should solar and battery ROI be on one calculator? A: Yes — they share most inputs (usage, tariffs, feed-in rate, discount rate) and the most useful question is what a battery adds on top of solar. This tool keeps them together with a mode switch so you can evaluate solar alone, solar with a battery, or a battery retrofit to existing solar without re-entering data. Q: Does the calculator account for electricity price rises and panel degradation? A: Yes — optional advanced assumptions let you escalate the electricity tariff each year (e.g. 2–5%/yr) and fade system output year-on-year (e.g. 0.5%/yr panel degradation). Leave both at 0% for a level, conservative baseline. Price escalation shortens the payback period while degradation slightly lengthens it; the cash-flow projection and break-even point update for whichever assumptions you set. Q: What is a good solar payback period in Australia? A: For a well-sized rooftop system with a healthy self-consumption share, 4 to 7 years is typical in 2026. Anything under about 5 years is excellent, and under 7 years is still a strong return given panels last 25+ years. Payback is shortest where you use most of your generation yourself (high self-consumption), your import tariff is high and the installed price after STCs is competitive. Q: How do you calculate solar return on investment? A: ROI = (lifetime savings − net installed cost) ÷ net installed cost, expressed as a percentage. The annual savings come from self-consumed generation valued at your import rate plus exported generation valued at the feed-in tariff. The ElecAS calculator reports ROI% alongside simple payback, discounted payback, NPV and IRR so you can judge the investment by whichever measure suits a household or commercial decision. Q: Is a home battery worth it in Australia in 2026? A: It is closer than it has ever been. The federal Cheaper Home Batteries program lowers the upfront cost and rising import tariffs raise the value of each stored kilowatt-hour, but a battery still rarely pays back on energy arbitrage alone. The deciding number is the marginal value of each stored kWh — roughly (round-trip efficiency × import rate − feed-in tariff) — multiplied by the cycles the battery actually achieves. Use the Battery Retrofit or Solar + Battery mode to test it on your own tariffs. Q: Why is self-consumption more important than feed-in tariff? A: Because grid import rates (around 25–45 c/kWh) are now several times higher than feed-in tariffs (around 3–8 c/kWh). Every kilowatt-hour you consume at the moment it is generated avoids buying grid power at the high import rate, whereas an exported kilowatt-hour only earns the low feed-in rate. Raising self-consumption — through usage timing or a battery — is the single biggest lever on solar payback, which is why the calculator weights savings by your self-consumption share. Q: Should I deduct the STC rebate before entering the system price? A: Yes. Enter the installed price net of all rebates — deduct STCs and any battery incentive such as Cheaper Home Batteries yourself. Because rebate schemes change frequently and vary by state, keeping them out of the model means the payback, NPV and IRR always reflect the real out-of-pocket price and do not go stale when a scheme is updated. Q: What discount rate should I use for a solar NPV calculation? A: Use a rate that reflects your alternative use of the money. For a household, 3–5% (roughly an offset account or term deposit) is reasonable; for a business, use your weighted average cost of capital, often 6–10%. A positive NPV at your chosen rate means the system beats that benchmark. IRR tells you the break-even discount rate so you can compare the project directly against other investments. Q: Does this solar ROI calculator work for New Zealand? A: Yes. Auckland, Wellington and Christchurch are included with PVGIS-derived specific yields, and you can enter NZ buy-back rates and import tariffs directly. The payback, NPV, IRR and cash-flow methodology is identical — only the tariffs, rebates and specific yield differ by location. ## LED Inrush Current Calculator URL: https://elecas.com.au/calculator/led-inrush Find the maximum number of LED fittings you can safely connect to a single MCB using the industry-standard proof-factor method. Inputs are the driver peak inrush Ipk, pulse width T50, fitting wattage and MCB rating; the calculator returns max fittings (inrush-limited and wattage-limited) and shows every step. Who it is for: Electrical engineers, lighting designers, contractors and electricians specifying MCBs for LED lighting circuits in Australian and New Zealand commercial, industrial and residential installations. Standards: AS/NZS 60898.1; IEC 60898-1; AS/NZS 3000:2018 Key capabilities: - Proof-factor (k) method — the industry-standard pulse-response approach used by Siemens, ABB, Schneider, Eaton and the Stantec spreadsheet template. - Built-in k(T50) chart digitised from the Siemens 5SY proof-factor curve, with log-interpolation between anchor points. - Type B / C / D one-click presets auto-populate the MCB magnetic-trip multiplier n (4 / 8 / 15) — editable for the specific MCB datasheet. - Two binding limits computed in parallel: inrush limit (N_inrush = ⌊k·n·In ÷ Ipk⌋) and wattage limit (N_wattage = ⌊In ÷ I_fit⌋) — answer is the smaller of the two. - Driver-efficiency-based per-fitting current: I_fit = P ÷ (V × η), matching how Australian lighting designers size circuits in practice. - Per-field guidance with info modals explaining exactly where to find Ipk and T50 on the LED driver datasheet. - Full step-by-step working shown in the result so the calculation is auditable and reviewable. - Export a branded PDF report with project header, inputs, calculation steps, max fittings and method / standards references. How to use: How to calculate the maximum number of LED fittings on an MCB 1. Find the driver peak inrush (Ipk) — Open the LED driver datasheet and locate the "Inrush current" or "Ipk" entry — use the value quoted at 230 V AC (typically 18–75 A per driver). 2. Find the pulse width (T50) — On the same datasheet locate the pulse width at 50 % of Ipk — usually labelled T50 or "Pulse width at 50 % Ipk", typically 100–600 µs. If not published, use 250–300 µs as a conservative default. 3. Enter the fitting wattage and driver efficiency — Fitting wattage P is the lamp output power (W). Driver efficiency η is typically 0.80–0.95; use 0.85 if unknown. 4. Select the MCB rating and curve — Pick the breaker rated current In from the standard ladder (2–125 A) and click Type B, C or D to auto-fill the magnetic trip multiplier n (4, 8 or 15). Override n if the MCB datasheet publishes a specific value. 5. Read the maximum number of fittings — The headline result is the smaller of the inrush limit and the wattage limit. The calculation steps panel shows k, the trip threshold k·n·In, the per-fitting current, and both limit counts, with the binding constraint highlighted. ### LED Inrush Sizing Guide — Proof-Factor Method (AS/NZS 60898) #### Why LED lighting circuits nuisance-trip MCBs Every modern LED driver contains an input bulk capacitor that has to charge from 0 V to the peak line voltage in a few hundred microseconds at switch-on. The instantaneous current to charge that capacitor — the peak inrush Ipk — is 10–250 A per driver, even though the driver's steady-state input current is well under 1 A. When several drivers on one circuit switch on synchronously the combined inrush briefly looks like a short-circuit to the MCB, and a curve B or even curve C breaker can trip on what is otherwise a perfectly healthy load. The traditional shortcut — comparing the inrush peak directly to the steady-state magnetic-trip threshold (3–5 × In for B, 5–10 × In for C, 10–20 × In for D) — is far too conservative for pulses that only last 100–600 µs. The MCB magnetic mechanism has a finite response time and the let-through I²t of a short pulse is too small to actuate it. The proof-factor method captures this and produces realistic maximum-fitting counts that match what installers actually see in service. #### The proof-factor (k) method explained Every major MCB manufacturer (Siemens 5SY, ABB S200, Schneider C60 / iC60, Eaton FAZ, NHP DOM) publishes a proof-factor chart that plots k = I_surge / I_hold as a function of pulse duration T50 on log-log axes. At T50 ≈ 10 µs the chart shows k ≈ 100 (a 100× peak can pass without tripping). At T50 ≈ 520 µs the chart drops to k = 5, and at T50 ≥ 10 ms it asymptotes to k = 1, where the pulse looks like a sustained fault. The Siemens 5SY chart is the de-facto industry reference and is digitised into this calculator with log-interpolation between anchor points. Multiplying k by the MCB's magnetic-trip multiplier n (a datasheet value — typically 4 for B-curve, 8 for C-curve and 15 for D-curve, midway through the AS/NZS 60898 tolerance band) and the rated current In gives the effective pulse trip threshold: I_trip = k × n × In. Divide that by the per-driver Ipk and you get the maximum number of fittings the MCB can withstand on a synchronous switch-on event. #### Why we also check the wattage (thermal) limit A 10 A Type-C MCB can absolutely survive a 600 A inrush pulse for 300 µs, but it cannot carry 600 A continuously — that would melt the cable and trip the breaker on thermal overload. The wattage limit converts the fitting wattage P to a steady-state input current I_fit = P ÷ (V × η) and divides the MCB rating by it. For an 82 W fitting at 230 V with η = 0.85, I_fit ≈ 0.42 A, so a 10 A MCB carries roughly 23 fittings continuously. The final answer is the lower of the two limits — almost always inrush for short low-wattage drivers, but wattage for larger drivers (HLG-240 and similar) where the steady-state current dominates. #### Worked example — 82 W fitting on a 10 A Type-C MCB A common audit scenario: a UFO highbay fitting with a published Ipk of 50.5 A and T50 of 300 µs, 82 W output, 0.85 driver efficiency on a 10 A Type-C MCB (n = 8). Step 1: read k(300 µs) = 8.7 from the chart. Step 2: I_trip = 8.7 × 8 × 10 = 696 A. Step 3: N_inrush = ⌊696 ÷ 50.5⌋ = 13 fittings. Step 4: I_fit = 82 ÷ (230 × 0.85) = 0.419 A. Step 5: N_wattage = ⌊10 ÷ 0.419⌋ = 23 fittings. Step 6: max fittings = min(13, 23) = 13 — limited by inrush. Note that the older "compare 600 A peak to 5×10 = 50 A trip threshold" method would have allowed only 1 fitting on the same breaker. The proof-factor method correctly delivers 13. This is why the same circuit that fails the conservative check works flawlessly in practice. #### Common LED driver inrush figures (verify against your specific datasheet) Tridonic LCI 30 W compact: Ipk ≈ 18 A, T50 ≈ 230 µs. Tridonic LCA 75 W linear: Ipk ≈ 38 A, T50 ≈ 250 µs. OSRAM Optotronic OT 30 W: Ipk ≈ 22 A, T50 ≈ 200 µs. OSRAM OT 75 W: Ipk ≈ 42 A, T50 ≈ 250 µs. Philips Xitanium 36 W: Ipk ≈ 25 A, T50 ≈ 250 µs. Philips Xitanium 75 W: Ipk ≈ 45 A, T50 ≈ 300 µs. Mean Well ELG-100: Ipk ≈ 65 A, T50 ≈ 300 µs. Mean Well HLG-240H: Ipk = 75 A, T50 = 570 µs (per official datasheet). These are indicative midpoints — actual values vary by part number, batch and mains voltage. Always use the value quoted at 230 V AC on the specific driver datasheet for design submissions. ### Frequently asked questions Q: Why do LED drivers cause MCBs to trip on switch-on? A: Every LED driver contains an input bulk capacitor that has to charge from 0 V to the peak line voltage in a few hundred microseconds at switch-on. The instantaneous current to charge that capacitor is 10–250 A per driver, even though the steady-state current is well under 1 A. When several drivers switch synchronously the combined inrush peak can exceed an MCB magnetic-trip threshold and cause a nuisance trip. Q: What is the proof factor k in LED inrush sizing? A: The proof factor k(T50) is a pulse-duration multiplier read from the MCB manufacturer chart — Siemens 5SY, ABB S200, Schneider C60 and Eaton FAZ all publish similar curves. It expresses how much higher than the steady-state magnetic trip threshold a short pulse can be before the MCB trips. At T50 = 100 µs, k ≈ 20; at 300 µs, k ≈ 9; at 520 µs, k = 5; at 10 ms, k = 1. Multiply k by the magnetic trip multiplier n and the MCB rating In to get the effective inrush trip threshold I_trip = k × n × In. Q: How many LED fittings can I connect to one MCB? A: Take the smaller of two limits. Inrush limit: N_inrush = ⌊k × n × In ÷ Ipk⌋ — k is read off the proof-factor chart at the driver T50, n is the MCB magnetic trip multiplier (4 / 8 / 15 for B / C / D), In is the MCB rating, and Ipk is the per-driver peak inrush. Wattage limit: N_wattage = ⌊In ÷ I_fit⌋ where I_fit = P ÷ (V × η). The final answer is min(N_inrush, N_wattage). Q: What is the difference between Type B, C and D MCB curves for LED lighting? A: AS/NZS 60898.1 (= IEC 60898-1) defines three magnetic-trip bands: Type B trips between 3 and 5 × rated current, Type C between 5 and 10 × In, and Type D between 10 and 20 × In. Type B is for residential and resistive loads, Type C is the default for commercial LED lighting because it tolerates the inrush of typical drivers, and Type D is reserved for very high-inrush loads such as transformers. The mid-band magnetic trip multipliers (n = 4, 8 and 15 respectively) are the default proof-factor inputs in this calculator. Q: Where do I find Ipk and T50 on an LED driver datasheet? A: Both values are listed in the "Input" or "Electrical characteristics" section of the driver datasheet. Typical labels are "Inrush current Ipk = 30 A at 230 V AC" and "Pulse width at 50 % Ipk (T50) = 250 µs". Tridonic, OSRAM, Philips Xitanium and Mean Well all publish them. Use the value quoted at 230 V AC — Ipk scales with mains voltage. If the datasheet only quotes Ipk, default T50 to 250–300 µs as a conservative starting point. Q: Is the proof-factor method only valid for Siemens MCBs? A: No. ABB S200, Schneider C60 / iC60, Eaton FAZ and NHP DOM all publish proof-factor curves with the same shape; the Siemens 5SY chart is widely treated as the industry reference. Curves vary slightly between manufacturers — for design-critical sign-off cross-check against the specific MCB datasheet. The k(T50) lookup in this calculator is digitised from the Siemens 5SY curve with the example anchor T50 = 520 µs → k = 5. Q: Is "compare peak inrush to magnetic trip threshold" the same as the proof-factor method? A: No, and the older comparison is far too conservative. Comparing peak inrush to the steady-state magnetic trip threshold (3–5, 5–10 or 10–20 × In) ignores pulse duration entirely — a 600 A pulse for 300 µs has very different let-through energy from 600 A sustained, and the MCB magnetic mechanism cannot react quickly enough to trip on the short pulse. The proof-factor k captures this and produces realistic counts that match what installers see in service. Q: Which Australian Standards apply to LED lighting circuit protection? A: AS/NZS 3000:2018 (Wiring Rules) sets the overall installation and protection requirements including overcurrent protection, voltage drop and cable sizing. AS/NZS 60898.1 (equivalent to IEC 60898-1) defines the MCB tripping characteristics — curves B, C, D — used by this calculator. Manufacturer datasheets remain the source of truth for individual driver inrush figures, and the engineer of record is responsible for matching breaker curve and rating to the installed driver population. ## EleCAD — Free Online Single Line Diagram Builder URL: https://elecas.com.au/elecad EleCAD is a free, browser-based single line diagram (SLD) builder for Australian electrical designers, electricians, contractors and project teams. Draw and edit electrical single line diagrams online with no install, no licence file and no plug-ins — just open the browser and start placing switchboards, loads, sources, protection devices and cables. EleCAD models the real electrical relationships between components, not just lines on a page: every connection carries cable data, every switchboard tracks its busbars and incomers, every protective device records its trip settings, and every load contributes to the upstream maximum demand. The tool is built for the way Australian electrical design actually works — main switchboards and distribution boards, sub-mains and final subcircuits, three-phase and single-phase, MCBs, MCCBs, RCDs and HRC fuses, copper and aluminium conductors, V-75 and X-90 insulation. Diagrams stay live: change a downstream load and the upstream demand updates; change a cable run and the voltage drop check follows. Export to PDF for design submissions, project files and client review, or export to DXF to open the diagram directly in AutoCAD, Revit and BricsCAD as fully editable CAD vectors — layers, symbols, cables and labels intact. EleCAD pairs natively with the rest of the ElecAS calculator suite — cable size, voltage drop, maximum demand (Tables C1, C2, C3), conduit sizing, generator sizing, UPS battery sizing — so the diagram and the calculations stay in lock-step. A practical alternative to AutoCAD Electrical, ETAP, EasyPower and SmartDraw for early-stage design, concept SLDs, tender drawings and small-to-medium project documentation. Who it is for: Australian electrical engineers, designers, electricians, contractors, estimators, building services consultants and project managers building or reviewing single line diagrams, switchboard concepts and early-stage electrical documentation. Standards: AS/NZS 3000:2018 (Wiring Rules); AS/NZS 3008.1.1:2025 (cable sizing references); Australian electrical drawing conventions Key capabilities: - Free, online, browser-based — no install, no licence file, no plug-ins. Open any modern browser and start drawing. - Drag-and-drop palette for sources, switchboards, distribution boards, loads, motors, generators, transformers and protective devices. - Model real electrical relationships, not just lines — every connection carries cable data and feeds into demand and voltage-drop calculations. - Switchboard editor with general settings, busbar configuration, incomer / main switch settings, and outgoing device schedules. - Protection device library — MCB curves B / C / D, MCCB, RCD, RCBO, HRC fuses — with editable trip settings and discrimination context. - Cable editor with copper / aluminium, V-75 / X-90, single-phase / three-phase, length, installation method and live AS/NZS 3008 sizing checks. - Links directly into the ElecAS calculator suite — cable size, voltage drop, maximum demand (Tables C1, C2, C3), generator sizing, UPS battery sizing. - Export single line diagrams to PDF for design submissions, tender packages, client review and project documentation. - Export to DXF (AutoCAD, Revit, BricsCAD) as fully editable CAD vectors — layers, symbols, cables and labels — so your drafting team drops the SLD straight into their sheets. - Tutorial mode walks first-time users through placing a source, switchboard, downstream loads, and exporting the diagram to PDF and DXF. - A practical alternative to AutoCAD Electrical, ETAP, EasyPower, SmartDraw and Lucidchart for early-stage Australian electrical design. ### Frequently asked questions Q: What is a single line diagram? A: A single line diagram (SLD), also called a one-line diagram, is a simplified schematic of an electrical power system that shows components — sources, switchboards, protective devices, cables and loads — using single lines and standard symbols instead of separate phase conductors. SLDs are the primary design and reference document for electrical installations in Australia, used for design submissions, tender drawings, switchboard schedules, commissioning and as-builts. Q: Is EleCAD free? A: Yes — EleCAD is free to use in your browser. You can build, edit and export single line diagrams without an account for the standard workflow. Pro features (saving projects to the cloud, larger diagrams, project history) are available on a paid plan. Q: Does EleCAD work in the browser without installing software? A: Yes. EleCAD runs entirely in the browser — Chrome, Edge, Safari and Firefox are all supported. There is nothing to download, no licence file to install, and no plug-in to enable. Diagrams are rendered locally so it works on any laptop, including locked-down corporate machines. Q: Can I export EleCAD single line diagrams to PDF or DXF? A: Yes. EleCAD exports your single line diagram to a clean, branded PDF suitable for design submissions, tender packages, client review and project files — the PDF includes the diagram, project details and a switchboard / device schedule. It also exports to DXF, which opens directly in AutoCAD, Revit, BricsCAD and other CAD packages as fully editable vector geometry (layers, symbols, cables and labels), so your drafting team can drop the SLD straight into their sheets. Q: EleCAD vs AutoCAD Electrical — what is the difference? A: AutoCAD Electrical is a heavyweight desktop CAD package licensed per seat — it is excellent for detailed schematics, panel layouts and large industrial projects but has a steep learning curve and high cost. EleCAD is a free, browser-based SLD builder focused on Australian single line diagrams and early-stage design — quick to learn, no install, and integrated with the ElecAS calculator suite. EleCAD is the right tool for concept SLDs, tender drawings, small-to-medium projects and any time AutoCAD would be overkill. The two also work together: EleCAD exports to DXF, so you can draft an SLD in the browser in minutes and open it in AutoCAD as fully editable geometry to finish it off. Q: EleCAD vs SmartDraw or Lucidchart for single line diagrams? A: SmartDraw and Lucidchart are general-purpose diagramming tools — they have electrical symbol libraries but no electrical engineering intelligence. EleCAD understands the actual electrical relationships: switchboards have busbars and incomers, cables have conductor material and installation method, loads contribute to maximum demand, protective devices have trip curves. That makes EleCAD substantially faster for real electrical design, with fewer mistakes carried into the calculations. Q: What symbols and components does EleCAD support? A: EleCAD includes the common Australian SLD symbols: utility supply, transformer, generator, UPS, main switchboard, distribution boards, switches, isolators, MCBs, MCCBs, RCDs, RCBOs, HRC fuses, motors, lighting loads, socket loads, mechanical loads and EV charging. New symbols are added based on user requests via the Contact page. Q: Does EleCAD link to cable sizing and maximum demand calculations? A: Yes. Every cable in EleCAD carries the inputs needed for AS/NZS 3008 cable sizing (conductor, insulation, installation method, length, design current) and every load feeds into the AS/NZS 3000 Table C1 / C2 maximum demand calculation upstream. You can jump from a diagram element straight into the relevant ElecAS calculator with the inputs prefilled. Q: Can I share or collaborate on diagrams? A: Diagrams are exported as PDF for sharing today. Real-time multi-user collaboration is on the roadmap — sign in to your ElecAS account to be notified when it ships. Q: Is EleCAD suitable for AS/NZS 3000 design submissions? A: EleCAD is suitable for the single line diagram component of an AS/NZS 3000 design submission, tender package or as-built drawing set. As with any electrical design tool, the user remains the engineer of record — every diagram, calculation and design decision must be reviewed and signed off by a qualified electrical professional before issue, construction or energisation. See the Verification page for the engineering review process behind ElecAS. ## EleCAD — Free PowerCAD Alternative for Australian Single Line Diagrams URL: https://elecas.com.au/powercad-alternative EleCAD is a free, user-friendly, browser-based alternative to PowerCAD for Australian electrical design. Where PowerCAD is older, desktop-only PC software with a steeper learning curve, EleCAD is a modern tool you can pick up in minutes. It is online single line diagram (SLD) software that builds AS/NZS 3000 single line diagrams from a drag-and-drop palette of sources, switchboards, distribution boards, protective devices, cables and loads. Unlike lines on a page, every element carries real electrical data — cables hold conductor, insulation and installation method for AS/NZS 3008.1.1 sizing, and loads feed maximum demand — and link straight into the AS/NZS 3000 and AS/NZS 3008 design calculators. Unlike a paid, installed desktop package, EleCAD runs in any browser with no licence file and exports a clean, branded PDF of the diagram. It is the practical choice for single line diagrams and design documentation on projects of any size — a bigger project simply means a bigger diagram, and EleCAD scales to it; heavier desktop tools like PowerCAD remain suited to detailed protection discrimination and graphical time–current coordination on more complex projects. The deciding factor is the complexity of the analysis, not the size of the project. Who it is for: Australian electrical engineers, designers, electricians, estimators and contractors evaluating PowerCAD or comparing electrical design software, and anyone looking for a free, no-install single line diagram tool for AS/NZS 3000 and AS/NZS 3008 design. Standards: AS/NZS 3000:2018 (Wiring Rules); AS/NZS 3008.1.1:2025 (Cable Selection); AS/NZS 4777.1 (Grid Connection — voltage rise) Key capabilities: - Free, browser-based alternative to PowerCAD — no install, no licence file, no per-seat cost. - Modern and user-friendly — learn it in minutes, where PowerCAD is older desktop software with a steeper learning curve. - Builds AS/NZS 3000 single line diagrams from a drag-and-drop palette of sources, switchboards, devices, cables and loads. - Models real electrical relationships — cables carry AS/NZS 3008 sizing data and loads feed maximum demand, not just lines on a page. - Links straight into the AS/NZS 3008 and AS/NZS 3000 design calculators, so the diagram and the calculations stay in step. - Exports a clean, branded PDF of the single line diagram for tender drawings, design submissions and project files. - Exports to DXF for AutoCAD, Revit and BricsCAD as fully editable CAD geometry — hand the SLD to your drafting team without redrawing it. - Scales to projects of any size — a bigger project just means a bigger single line diagram; the deciding factor is analysis complexity, not project size. - Honest fit: PowerCAD remains stronger for deep protection discrimination and graphical time–current (TCC) studies on more complex projects. How to use: How to build a single line diagram in EleCAD 1. Open EleCAD in your browser — Go to EleCAD and start a new project — there is nothing to install, no licence file and no admin rights required. It runs in Chrome, Edge, Safari or Firefox on any laptop. 2. Add a source — Drag a source (utility or substation) onto the canvas and set its rating — amps for a utility supply or kVA for a substation. EleCAD uses it to establish the fault level and earth loop impedance for everything downstream. 3. Add a switchboard — Drag a switchboard onto the canvas and configure its busbar sections, incomer / main switch and outgoing protective devices. Devices auto-size to the connected load, or you can set them manually. 4. Add loads and cables — Add motor, socket and general loads and connect them. Each cable carries conductor material, insulation, installation method and length, so it can be sized correctly. 5. Let EleCAD size and check — EleCAD sizes each cable to AS/NZS 3008.1.1, aggregates maximum demand to AS/NZS 3000, and checks voltage drop, earth fault loop impedance and protection coordination live as you build. 6. Export the branded PDF — Review the live design-issues panel, fill in the project metadata, and export a branded PDF of the single line diagram with cable and switchboard schedules for your submission or tender package. ### PowerCAD alternative — how EleCAD compares for Australian electrical design #### What EleCAD is (and how it differs from PowerCAD) EleCAD is a free, browser-based single line diagram (SLD) builder for Australian and New Zealand electrical design, built to AS/NZS 3000:2018 and AS/NZS 3008.1.1:2025 conventions. You place sources, switchboards, distribution boards, protective devices, cables and loads from a drag-and-drop palette, and every element carries real electrical data: cables hold conductor material, insulation and installation method for AS/NZS 3008 sizing, switchboards track busbars and incomers, protective devices record their trip settings, and loads contribute to the upstream maximum demand. Those inputs link straight into the AS/NZS 3008 and AS/NZS 3000 design calculators, so the diagram and the calculations stay in step. PowerCAD is an established, paid desktop power-systems package. The core difference is delivery, ease of use and depth: EleCAD is a modern, user-friendly browser tool with no install or licence file — free and quick to learn — focused on concept single line diagrams and fast design; PowerCAD is older, desktop-only PC software with a steeper learning curve, aimed at detailed, large-project power-systems modelling. #### PowerCAD vs EleCAD — choosing the right tool Choose EleCAD when you want immediate, no-install single line diagrams and standards-referenced design from any laptop, free, with a clean PDF of the diagram — for concept SLDs, tender drawings and projects of any size, since a bigger project simply means a bigger diagram and EleCAD scales to it. Choose a heavier desktop package like PowerCAD when the project needs deep protection discrimination, graphical time–current coordination, or full modelling of a complex distribution network. The deciding factor is the complexity of the analysis, not the size of the project — EleCAD does not try to replace that class of tool, and many engineers use EleCAD for everyday design across projects of every size and reach for a desktop package only when the analysis genuinely requires it. ## About ElecAS URL: https://elecas.com.au/about Learn about the ElecAS platform, its creator and the goals behind the electrical calculator suite. Who it is for: Users who want platform background, product intent and creator context. Key capabilities: - Explain the purpose and origin of the ElecAS platform. - Provide supporting trust signals for the calculator suite. - Link back into the main tools directory and contact path. ### About ElecAS — a practitioner-built Australian electrical design suite #### What ElecAS is ElecAS is a free suite of electrical design calculators built specifically for the Australian and New Zealand framework — AS/NZS 3000:2018 (the Wiring Rules) and AS/NZS 3008.1.1:2025 (cable selection). It covers the everyday design workflows: maximum demand (Tables C1, C2 and C3), cable selection and sizing, voltage drop and voltage rise, conduit and cable tray fill, earthing conductor sizing, current-carrying-capacity derating, power factor correction, UPS battery and generator sizing, and lighting design. Every calculator runs in the browser with no sign-up and no paywall on the core calculation, and each result can be exported as a citation-rich PDF report that references the specific clause, table and formula behind the number — written to drop straight into a design submission or verification package. #### Why ElecAS exists Most general-purpose electrical calculators are built around international defaults and leave the engineer to reconcile them with the local standard by hand. ElecAS takes the opposite approach: it encodes the actual AS/NZS tables, formulae and worked examples directly, so the method on screen is the method in the standard. The goal is to make standards-correct Australian electrical design faster to produce and easier to check, without sacrificing traceability. #### Standards-first by design Each calculator is implemented from the primary standard rather than a second-hand summary, with the calculation logic separated from the interface as a pure, deterministic engine. Cable selection works against the current-rating, AC-resistance, reactance and grouping tables of AS/NZS 3008.1.1:2025; maximum demand follows AS/NZS 3000:2018 Appendix C; voltage rise references AS/NZS 4777 where inverter logic applies. The same engine that produces the on-screen value produces the value in the exported PDF, so there is no display-only rounding hidden between the two. The calculation engines are covered by automated tests that run against the real checked-in standard reference tables on every change, and the methodology is documented in full on the Verification page. #### Who builds ElecAS ElecAS is designed, built and reviewed by Wisam Tozah, a practising electrical engineer based in Sydney, Australia — B.Eng (Electrical), MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC Engineer and IntPE(Aus). It is a practitioner tool: the same calculations it performs are the ones run on real Australian projects, and every calculator is reviewed against the source standard before release. ## Meet the Creator of ElecAS URL: https://elecas.com.au/creator ElecAS is designed, built and reviewed by Wisam Tozah, a chartered professional electrical engineer (CPEng, NER, MIEAust) based in Sydney, Australia. Who it is for: Engineers, reviewers and clients checking the qualifications and engineering judgement behind the ElecAS calculators. Key capabilities: - Standards-first: every calculator traces back to the relevant clause in AS/NZS 3000:2018 or AS/NZS 3008.1.1:2025. - Practitioner-built: created by an engineer who runs the same calculations on real projects. - Full credentials: B.Eng (Electrical), MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE(Aus). ### Wisam Tozah — the electrical engineer behind ElecAS #### Who builds ElecAS ElecAS is designed, built and reviewed by Wisam Tozah, a practising electrical engineer based in Sydney, Australia. Rather than a generic calculator wrapped around international defaults, ElecAS is a practitioner tool — the same maximum demand, cable sizing, voltage drop and earthing calculations it performs are the ones run day to day on real Australian electrical projects. #### Credentials and registration Wisam holds a Bachelor of Engineering (Electrical) and is a Member of Engineers Australia (MIEAust), a Chartered Professional Engineer (CPEng) and listed on the National Engineering Register (NER). He is registered as a NSW Design and Building Practitioner (DBP) and NSW Professional Registered Engineer (PRE), and holds APEC Engineer and International Professional Engineer — IntPE(Aus) — recognition. These registrations sit behind the engineering judgement in ElecAS: every calculator is traced back to the relevant clause in AS/NZS 3000:2018 or AS/NZS 3008.1.1:2025 and reviewed before it reaches production. #### Why a practising engineer built ElecAS ElecAS started from the work itself — running the same standards calculations repeatedly across projects and wanting them faster, traceable and consistent. Building the suite as a practitioner means the calculators are shaped by how the standards are actually applied on site and in design submissions, not just by the letter of the formula. Each tool exposes the inputs, intermediate values and the clause or table it relied on, so a reviewer can re-trace the result by hand. #### Engineering responsibility ElecAS is a design aid for qualified electrical professionals, not a substitute for one. It confirms that the calculation method and its implementation are correct, but the user remains the engineer of record — responsible for selecting the right method, validating inputs and confirming results against current standards and project conditions before issue, construction, energisation or certification. The Verification page documents the testing and review process in detail. ### Frequently asked questions Q: Who created ElecAS? A: ElecAS is created and maintained by Wisam Tozah, an Associate Electrical Engineer based in Sydney, Australia, holding B.Eng (Electrical), CPEng, NER, MIEAust, NSW DBP, NSW PRE, APEC and IntPE(Aus) credentials. He builds and reviews every calculator against the primary Australian Standards. Q: Are the ElecAS calculators reviewed by a qualified engineer? A: Yes. Every calculator is implemented from the relevant Australian Standard, validated against worked examples and reviewed by a Chartered Professional Engineer (CPEng) before release. The Verification page documents the testing and review process in detail. ## ElecAS Pricing — Free, Pro and Team URL: https://elecas.com.au/pricing All ElecAS calculators are free to use with PDF export and no sign-up. The Pro plan adds cloud save and sync, unlimited saved calculations, custom logo and branding on PDF reports, and project workspaces. Who it is for: Engineers, contractors and consultancies comparing free and paid electrical design tools for Australian standards work. Key capabilities: - Free plan: every AS/NZS calculator, PDF export and print, save calculations to your device — no account needed. - Pro plan: cloud save and sync across devices, unlimited saved calculations, custom logo and accent colour on PDF reports, project workspaces and priority support. - Team plan for consultancies and contractors with shared branding and collaboration. ### Frequently asked questions Q: Is ElecAS free to use? A: Yes. Every ElecAS calculator — cable sizing, voltage drop, maximum demand, conduit and cable tray sizing, earthing, power factor correction, generator sizing, UPS battery sizing and more — is completely free, including PDF export. No account or sign-up is required to calculate. Q: What does ElecAS Pro add over the free plan? A: Pro adds cloud save and sync across devices, unlimited saved calculations, removal of ElecAS branding from PDF reports, your own company logo and accent colour on reports, project workspaces with folders, and priority email support. Q: Do I need an account to use the calculators? A: No. All calculators work without an account. An account is only needed if you want to save calculations to the cloud, sync between devices or apply custom branding to PDF reports. ## ElecAS Changelog URL: https://elecas.com.au/changelog Follow ElecAS development — every calculator update, standards amendment review, new tool and fix is published here, grouped by release date. Who it is for: Users tracking calculator updates, standards amendment handling and new feature releases. Key capabilities: - Every release is version-controlled and listed by date. - Standards amendments and calculation fixes are documented as they ship. - Historical results can be traced to the specific build that produced them. ## Contact ElecAS URL: https://elecas.com.au/contact Contact ElecAS for support, bug reports, calculator questions and product feedback. Who it is for: Users needing support, reporting bugs or sending feedback about a calculator or tool. Key capabilities: - Provide a clear support route for calculator questions and bug reports. - Support trust and user assistance signals across the public site. - Connect users back to the relevant calculators after they make contact. ## ElecAS Terms of Use URL: https://elecas.com.au/terms Read the terms of use that apply to the ElecAS electrical design and calculator platform. Who it is for: Users reviewing legal terms and platform usage conditions. Key capabilities: - Provide access to the platform terms of use. - Support transparency for public users and clients. - Remain available as a standard legal/support page. ## ElecAS Privacy Policy URL: https://elecas.com.au/privacy Read how ElecAS handles privacy, analytics, and website data collection. Who it is for: Users reviewing privacy, analytics and data handling information. Key capabilities: - Explain privacy and analytics handling for the ElecAS website. - Support transparency and trust across the public product. - Keep legal pages aligned with the same canonical URL pattern as the rest of the site. ## ElecAS Calculation Verification URL: https://elecas.com.au/verification Read how ElecAS verifies its calculators against Australian Standards, what testing and review are in place, and where engineering responsibility begins. Who it is for: Engineers, designers, estimators and reviewers assessing the trustworthiness of ElecAS calculation outputs before relying on them for design, procurement, construction or certification. Standards: AS/NZS 3000:2018; AS/NZS 3008.1.1:2025; AS/NZS 4777 Key capabilities: - Explain how each calculator is built directly from primary Australian Standards. - Document the pure calculation engine architecture used across the suite. - Cover automated unit tests, worked-example validation, and qualified engineering review. - Describe how amendments and user feedback feed back into the calculators. - Set a clear boundary between verification, professional certification, and legal liability. ### How ElecAS verifies its electrical calculators against AS/NZS 3000 and AS/NZS 3008.1.1 #### How ElecAS calculations are verified Every ElecAS calculator is implemented directly from the primary Australian Standard or first-principles formula for that workflow — not from second-hand summaries or undocumented rules of thumb. The calculation logic is deliberately separated from the user interface as a pure, deterministic engine (each tool stores its formulae and reference tables in dedicated calculations.ts and constants.ts modules), so the exact code path that produces the on-screen number also produces the value in the exported PDF report. There is no display-only rounding hidden between the engine and the result. Verification rests on four layers: implementation straight from the source standard, automated unit tests that lock in expected outputs, cross-checks against worked examples in the standard and recognised reference handbooks, and review by a qualified electrical engineer before any new calculator or material change reaches production. #### Automated testing — {{TESTS}} tests across {{ENGINES}} calculation engines ElecAS carries {{TESTS}} automated Vitest tests with {{ASSERTIONS}} expected-value assertions across {{FILES}} test suites covering the core calculation engines. These tests run on every code change and fail the build on any regression, so a calculator cannot silently drift from its expected output between releases. Critically, the tests do not use mocked numbers. They run the real calculation engine against the same checked-in standard reference tables the live application loads at runtime — for example the AS/NZS 3008.1.1:2025 impedance and current-carrying-capacity tables. The tests assert that the engine reads the correct table (for instance aluminium single-core resistance from Table 4.5(B), not the copper Table 4.5(A)), reproduces the standard formula Vd = K × Zc × I × L / 1000, and that missing table rows are forced to flag as unavailable rather than silently returning a value. #### Which calculators are unit-tested Dedicated automated test suites guard the Cable Sizing, Voltage Drop, Voltage Rise, Maximum Demand (Tables C1, C2 and C3), Cable Tray, Conduit Sizing, protection / time-current-curve (TCC) and Lighting Design engines. The remaining calculators — including Earthing (Table 5.1) and Generator / UPS sizing — are worked-example validated against the source standard and engineering-reviewed before release. Every input that drives a result is shown on screen with its relevant clause or table reference, and the exported PDF report lists the inputs, the intermediate values (such as derated current-carrying capacity, mV/A·m, or itemised demand contributions) and the final design value — so any reviewer can re-trace the calculation by hand. #### Standards, amendments and version control The calculators are built against AS/NZS 3000:2018 (Wiring Rules, including Amendments 1 and 2), AS/NZS 3008.1.1:2025 for current-carrying capacity and voltage drop, AS/NZS 4777 where inverter and grid-connection logic applies, and manufacturer datasheets for protective device curves. When a standard is amended or republished, the affected engines and reference tables are reviewed and updated. Every change is version-controlled and listed in the in-app changelog, with a build version stamp, so any historical result can be traced to the exact build that produced it. ElecAS is built and reviewed by Wisam Tozah, an Associate Electrical Engineer (B.Eng Electrical, MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE(Aus)) practising in Sydney, Australia. #### The limit of verification Verification is not certification. ElecAS is a design aid for qualified electrical professionals: it confirms that the calculation method and its implementation are correct, but no automated check can account for every site condition, manufacturer quirk or project-specific constraint. The user remains the engineer of record and is responsible for selecting the correct method, validating inputs, and confirming results against the current standards and manufacturer data before issue, construction, energisation or certification. ### Frequently asked questions Q: How does ElecAS verify its calculations are accurate? A: Each calculator is implemented directly from the relevant Australian Standard or first-principles formulae, separated from the user interface as a pure calculation engine, validated against worked examples from the source standard and reference handbooks, and locked in with automated Vitest unit tests that prevent regressions on every code change. Q: Which standards do the ElecAS calculators reference? A: The calculators are built against AS/NZS 3000:2018 (Wiring Rules, including Amendments 1 and 2), AS/NZS 3008.1.1:2025 for current-carrying capacity and voltage drop, AS/NZS 4777 where inverter and grid-connection logic applies, and manufacturer datasheets for protective device curves used in the time-current curve tool. Q: Are ElecAS results certified or signed off by an engineer? A: No. ElecAS is a design aid for qualified electrical professionals — it does not provide engineering certification, professional advice, or assurance of compliance. The user remains the engineer of record and is responsible for validating every input, intermediate value, and final result against current standards and project conditions before issue, construction, energisation, or certification. Q: How are the calculators kept up to date with standards amendments? A: When an Australian Standard is amended or republished, the affected calculation engines and reference tables are reviewed and updated. Each release is version-controlled and listed in the in-app changelog so any historical result can be traced to the specific build that produced it. Q: What should I do if I find a result that disagrees with a worked example? A: Report it through the ElecAS Contact page with the inputs you used and the source of the comparison. Verification reports from practising engineers are treated as priority issues and feed directly into the calculator review and update process. Q: How many automated tests does ElecAS run on its calculators? A: ElecAS runs {{TESTS}} automated tests (with {{ASSERTIONS}} expected-value assertions) across {{FILES}} test suites covering {{ENGINES}} calculation engines. The tests run on every code change and fail the build on any regression. They run the real calculation engine against the same checked-in AS/NZS reference tables the live app loads at runtime — not mocked numbers — and assert correct table routing, correct formula reproduction, and that missing table rows flag rather than silently return a value. Q: Which ElecAS calculators are covered by automated tests? A: Dedicated automated test suites guard the Cable Sizing, Voltage Drop, Voltage Rise, Maximum Demand (Tables C1, C2 and C3), Cable Tray, Conduit Sizing, protection / time-current-curve (TCC) and Lighting Design engines. The remaining calculators, such as Earthing and Generator / UPS sizing, are worked-example validated against the source standard and engineering-reviewed before release. Q: Does ElecAS test against real standard data or simplified approximations? A: Real standard data. The automated tests load the same checked-in AS/NZS 3008.1.1 impedance and current-carrying-capacity reference tables that the live application uses at runtime, then assert the engine selects the correct table (for example aluminium single-core from Table 4.5(B), not the copper Table 4.5(A)) and reproduces the published formula. Where a table row is missing, the engine is forced to flag the result as unavailable rather than estimate. Q: How can I audit or reproduce an ElecAS result by hand? A: Every input that drives a result is shown on screen with its relevant clause or table reference. The exported PDF report lists the inputs, the intermediate values (such as derated current-carrying capacity, mV/A·m, or itemised demand contributions) and the final design value, plus the build version, so a reviewer can re-trace the entire calculation against the standard by hand. Q: Who builds and reviews the ElecAS calculators? A: ElecAS is built and reviewed by Wisam Tozah, an Associate Electrical Engineer practising in Sydney, Australia — B.Eng (Electrical), MIEAust, CPEng (Chartered Professional Engineer), NER (National Engineering Register), NSW DBP, NSW PRE, APEC Engineer and IntPE(Aus). New calculators and material changes are reviewed before they reach production. ## Useful Electrical Engineering Links URL: https://elecas.com.au/useful-links Browse useful external links used in everyday electrical engineering design and planning workflows. Who it is for: Users collecting practical external references used during electrical design and project planning. Standards: Project planning references; Authority and mapping links Key capabilities: - Access practical reference links used during electrical planning and coordination. - Use the page as a lightweight resource hub alongside the calculators. - Keep the route indexable and strongly linked from the homepage. ## Electrical Design Guides — Interactive AS/NZS & NCC Walkthroughs URL: https://elecas.com.au/design-guide A growing library of free, interactive electrical design guides for Australian and New Zealand engineers, electricians and designers. Each guide is a self-contained, step-by-step walkthrough of a real design task — the standard behind it, the method worked line by line, an interactive calculator to try your own numbers, a worked example and the compliance check. Current guides cover inverter and solar voltage rise to AS/NZS 4777.1, and emergency and exit lighting to AS/NZS 2293.1 and NCC 2022 Part E4. Every guide links straight to the matching ElecAS calculator for production design work and a branded PDF report. Who it is for: Australian and New Zealand electrical engineers, CEC accredited solar designers, licensed electricians, electrical designers and students learning the AS/NZS and NCC design framework. Standards: AS/NZS 4777.1:2016 (Grid connection of energy systems via inverters — voltage rise); AS/NZS 2293.1:2018 (Emergency escape lighting and exit signs — design); NCC 2022 Volume One Part E4 (Emergency lighting, exit signs and warning systems); AS/NZS 3008.1.1:2025 (Selection of cables — conductor impedance) Key capabilities: - Interactive, step-by-step design guides — read the method, then try it live in an embedded calculator. - Solar and inverter voltage rise to AS/NZS 4777.1 — the 2% limit, the formula worked line by line, and how to fix a failing design. - Emergency and exit lighting to AS/NZS 2293.1 and NCC 2022 Part E4 — where it is required, luminaire classification and spacing. - Each guide links to the matching ElecAS calculator for real project work and a branded PDF report. - Written and reviewed by a Chartered Professional Engineer (CPEng, NER). ## Voltage Rise Design Guide — How to Calculate Solar Inverter Voltage Rise to AS/NZS 4777.1 URL: https://elecas.com.au/design-guide/voltage-rise A step-by-step guide to inverter-path voltage rise for Australian solar PV and battery systems. Learn why AS/NZS 4777.1 Clause 3.3.3 caps the rise from the point of supply to the inverter a.c. terminals at 2% of nominal voltage (4.6 V single-phase, 8 V line-to-line three-phase), then work the calculation line by line: full-export current, cable impedance from AS/NZS 3008.1.1, the volt-drop coefficient Vc = K·Z, the per-segment rise and the total path percentage. An embedded interactive calculator lets you change the inverter, cables and route and watch every line update against the 2% limit, and the guide shows exactly how to fix a design that fails — upsize the worst cable, shorten the run, apply an export limit or switch to copper. Who it is for: CEC accredited solar designers and installers, electricians and electrical engineers learning or teaching the AS/NZS 4777.1 voltage rise check for grid-connected solar PV and battery inverters. Standards: AS/NZS 4777.1:2016 (Grid connection of energy systems via inverters — Clause 3.3.3 voltage rise); AS/NZS 4777.2:2020 (Inverter requirements — over-voltage response); AS/NZS 3008.1.1:2025 (Cable selection — conductor R and X impedance); AS 60038 (Standard voltages — 230 V / 400 V nominal) Key capabilities: - Understand the 2% AS/NZS 4777.1 limit and why voltage rise is the mirror image of voltage drop. - Work the formula one line at a time: current, impedance Z, volt-drop coefficient Vc = K·Z, per-segment rise, total %. - Interactive calculator with a live “voltage along the path” profile against the 2% ceiling. - See a failing design and the four ways to fix it — upsize, shorten, export-limit, or copper. - Links straight to the full ElecAS Voltage Rise calculator for multi-inverter projects and PDF reports. How to use: How to calculate solar inverter voltage rise under AS/NZS 4777.1 1. Find the full-export current — Convert the inverter rated kW to current: I = P × 1000 ÷ (√3 × V × pf) for three-phase, or P × 1000 ÷ (V × pf) for single-phase. Default power factor to unity unless the inverter injects or absorbs reactive power. 2. Read R and X for each cable — From AS/NZS 3008.1.1 read the a.c. resistance R and reactance X (Ω/km) for each cable size, material and installation method along the path. 3. Combine into an effective impedance — Use the worst-case magnitude Z = √(R² + X²), or Z = R·cosφ + X·sinφ at a set power factor. 4. Calculate the rise on each segment — Vc = K × Z (K = 2 single-phase, √3 three-phase), then V = length × current × Vc ÷ 1000 for each cable. 5. Sum the path and check against 2% — Add every segment’s rise, divide by the nominal voltage and express as a percentage. Pass if the total from the point of supply to the inverter terminals is 2% or less; if not, upsize the biggest contributor and re-check. ### How to calculate solar inverter voltage rise under AS/NZS 4777.1 #### What voltage rise is and why AS/NZS 4777.1 limits it to 2% When a grid-connected inverter exports active power, current flows the other way along the cable — from the inverter back through the final subcircuit, any submain, and the consumer mains toward the point of supply. The impedance of each conductor lifts the inverter terminal voltage above the nominal supply voltage. Voltage rise is the exact mirror image of voltage drop: the same resistance and reactance, the same run length, only the direction of power flow is reversed. AS/NZS 4777.1:2016 Clause 3.3.3 limits the rise from the point of supply to the inverter a.c. terminals to 2% of nominal voltage, evaluated at the rated current of the inverter energy system. On a 230 V single-phase supply that is about 4.6 V; on a 400 V three-phase supply it is about 8 V line-to-line. The limit is tight because the grid can already sit near the +10% steady-state ceiling (253 V on a 230 V system) — your rise stacks on top of it, and once the inverter terminal voltage nears the AS/NZS 4777.2 over-voltage response point it curtails or disconnects, quietly losing generation on the sunniest days. #### The voltage rise formula, one line at a time Step 1 — full-export current. Convert the inverter rating to the current the cable carries: I = P × 1000 ÷ (√3 × V × pf) for three-phase, or I = P × 1000 ÷ (V × pf) for single-phase. Default the power factor to unity unless the inverter is set to absorb or inject reactive power. Step 2 — effective impedance. From the AS/NZS 3008.1.1 tables read the conductor a.c. resistance R and reactance X in Ω/km for each cable. Combine them as the worst-case magnitude Z = √(R² + X²), or as R·cosφ + X·sinφ when a specific power factor is used. Step 3 — volt-drop coefficient. Vc = K × Z, where K = 2 for single-phase (active plus neutral) and K = √3 for balanced three-phase (the line-to-line factor). Step 4 — rise per segment. V = length × current × Vc ÷ 1000, applied to every cable in the path. Step 5 — total and compliance. Add the rise of each segment, divide by the nominal voltage and express as a percentage. The design passes when the total from the point of supply to the inverter terminals is 2% or less. #### A worked example — 15 kW three-phase rooftop solar A 15 kW three-phase inverter on a 400 V supply draws I = 15 × 1000 ÷ (√3 × 400) ≈ 21.7 A at full export. Run it through 30 m of 16 mm² copper consumer mains and a 25 m 10 mm² copper final subcircuit. The mains contributes about 1.30 V (0.32%) and the final subcircuit about 1.72 V (0.43%), for a total of roughly 3.0 V — about 0.75% of 400 V. That sits comfortably inside the 2% allowance, so the design passes. Change the inverter size, the cable sizes or the run lengths in the interactive calculator and every line of the working updates against the 2% ceiling. #### How to fix a design that fails the 2% limit A non-compliant result has four common levers, and you should always target the cable segment contributing the most volts first. Upsizing the worst cable is the usual fix — rise falls roughly in proportion to conductor cross-sectional area, so one or two sizes up on the dominant segment is often enough. Shortening the route helps in direct proportion to length — relocating the inverter or board closer to the point of supply can be cheaper than jumping cable sizes. A hard export limit reduces the current (and rise) in the shared consumer mains, though the final cable still carries full inverter output. Finally, copper has appreciably lower resistance than aluminium for the same size, so switching material can recover margin without a size increase. #### Voltage rise vs voltage drop The two checks use identical cable impedance and the same route method, but they are assessed separately and against different limits. Voltage drop (AS/NZS 3000:2018 Clause 3.6) applies to load-side circuits with a 5% total budget; voltage rise (AS/NZS 4777.1 Clause 3.3.3) applies to the inverter export path with a 2% limit. The same cable on the same installation has both — drop under maximum demand and rise under maximum export — so a solar retrofit onto an existing installation must satisfy both independently. ## Emergency Lighting Design Guide — AS/NZS 2293.1 & NCC 2022 Part E4 URL: https://elecas.com.au/design-guide/emergency-lighting A practical guide to designing compliant emergency and exit lighting for Australian buildings. Learn where emergency lighting is triggered by building classification and floor area under NCC 2022 Part E4, how to read a luminaire’s A–E classification under AS/NZS 2293.3, and how to set out fitting spacing from the AS/NZS 2293.1 spacing tables. An interactive spacing simulator lets you enter a corridor length and maximum spacing and see the coverage and the minimum number of fittings, alongside the specific locations that always need a luminaire and the stairway 1-lux rule. Who it is for: Australian electrical engineers, electricians, building designers, certifiers and fire-safety practitioners designing or checking emergency and exit lighting to AS/NZS 2293.1 and NCC Part E4. Standards: AS/NZS 2293.1:2018 (Emergency escape lighting and exit signs — system design, installation and operation); AS/NZS 2293.3 (Emergency escape luminaires and exit signs — luminaire classification); NCC 2022 Volume One Part E4 (Emergency lighting, exit signs and warning systems) Key capabilities: - Where emergency lighting is required by NCC 2022 Part E4 — building classification and floor-area triggers. - Reading a luminaire’s A–E classification under AS/NZS 2293.3 and how it maps to the spacing tables. - Setting out fitting spacing with an interactive coverage simulator to AS/NZS 2293.1. - The specific locations that always need a luminaire, and the stairway 1-lux rule. - Links to the ElecAS Lighting Design tool for full automated layouts. How to use: How to design emergency lighting spacing under AS/NZS 2293.1 1. Fix the classification and required areas — Determine the building classification and storey floor areas, then mark every zone where NCC 2022 Part E4 requires emergency lighting — paths of travel to exits, large rooms and all stairways. 2. Select the luminaire and read its class — Choose an emergency luminaire and read its A–E classification under AS/NZS 2293.3, which maps to a specific maximum-spacing table in AS/NZS 2293.1. 3. Read the maximum spacing from the table — Using the luminaire class and mounting height, read the maximum spacing for a general area (0.2 lux) or stairway / path of travel (1 lux). 4. Lay out fittings so coverage overlaps — Space fittings so their coverage circles overlap and reach walls at half-spacing, keeping every point above the required illuminance, and never let one luminaire serve more than 500 m². 5. Add specific-location and stairway fittings — Place a luminaire within 2 m of exit doorways, direction changes, corridor intersections and level changes, and provide 1 lux to every stair flight and landing. ### How to design emergency and exit lighting under AS/NZS 2293.1 and NCC Part E4 #### Where emergency lighting is required under NCC 2022 Part E4 The National Construction Code (NCC 2022 Volume One, Part E4) sets where emergency lighting must be provided, driven by building classification and floor area. Emergency lighting is required in every fire-isolated stairway, passageway and ramp, in every required non-fire-isolated stairway, and in the path of travel to an exit on storeys above a threshold floor area (typically 300 m² for Class 5, 6 and 9 buildings), among other triggers. The first design step is always to fix the building classification and the storey floor areas, then mark the required zones — corridors and paths of travel to exits, large rooms that do not open onto an already-lit space, and every stairway. Stairways carry emergency lighting in effectively every building, regardless of class. #### Reading a luminaire classification (Class A–E) Emergency escape luminaires are classified A to E under AS/NZS 2293.3 by the shape of their light distribution. Each class maps to its own maximum-spacing tables in AS/NZS 2293.1, and only the light within the geometric cut-off counts toward compliance. Practically, the classification plus the mounting height set the maximum spacing you are allowed between fittings for a general area (0.2 lux) or a stairway and path of travel (1 lux). Pick the fitting first, read its class and the matching spacing table, and only then lay out the fittings. #### Setting out fitting spacing to AS/NZS 2293.1 For a corridor or open area, the maximum spacing from the AS/NZS 2293.1 table for the luminaire class and mounting height gives the coverage diameter of each fitting. Lay fittings so their coverage circles overlap and reach the walls at half-spacing, so no point on the escape path falls below the required maintained illuminance. Two extra limits apply on top of the spacing table: a single luminaire must not serve more than 500 m² regardless of spacing (Clause 4.3), and the light loss factor (0.75 for maintained fittings) is applied in the photometric calculation. The interactive spacing simulator in this guide lets you enter a run length and the table maximum spacing and see both the coverage and the minimum number of fittings the run needs. #### Specific locations and stairways Beyond the spacing across open areas, AS/NZS 2293.1 requires a luminaire within 2 m of specific points where people make decisions or meet hazards — exit doorways, changes of direction, intersections of corridors, and changes of floor level (Clause 4.5). These points get a fitting even if the general-area spacing would not otherwise place one there. Stairways are treated separately: every flight and landing must receive at least 1 lux (Clause 4.8), using the higher-illuminance F-series spacing tables rather than the 0.2 lux general-area tables. Combined with the specific-location rule, this ensures the whole path of travel to a place of safety stays lit when normal supply fails.