What is the AS/NZS 4777.1 voltage rise limit for solar inverters in Australia?

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.

How is voltage rise calculated for a grid-connected solar PV inverter?

Per AC cable segment ΔU = K × I × (R·cosφ + X·sinφ) × L, where K = 2 for single-phase (active plus neutral return) and K = √3 for balanced three-phase, 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 at the insulation operating temperature, L is the cable route length in metres, and φ is the inverter operating power factor angle. At worst case the bracket is replaced by the impedance magnitude √(R² + X²). 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.

Does the 2% AS/NZS 4777.1 voltage rise limit include the consumer mains?

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.

How do I reduce voltage rise on a solar PV installation that fails the 2% limit?

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.

Does an export-limited inverter still have to satisfy the 2% voltage rise limit?

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 consumer mains only: the one segment beyond the export-limit measurement point, with the submains and each inverter cable still assessed at full output; otherwise size on the full IES rated current.

How does the calculator handle multiple inverters on the same installation?

Add each inverter with its own size, name and AC cable run; the connection point (MSB direct or via a DB) is set once for the installation and is shared by every inverter. The tool aggregates currents per segment: the consumer mains and, where used, the submain carry the sum of all inverters, while each inverter's own final subcircuit carries only its own current. The final pass/fail verdict checks the worst-case inverter path against the 2% AS/NZS 4777.1 limit.

What is the difference between voltage drop and voltage rise?

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, which sets a 5% limit from the point of supply to any point in the installation (a note to that clause allows more where supply comes from a substation forming part of the installation). 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.

Should I use worst-case power factor for AS/NZS 4777.1 voltage rise?

Yes, wherever the inverter is configured for any AS/NZS 4777.2 reactive response mode (volt-var, fixed PF other than unity, PF response), because the operating PF then moves with terminal voltage and is not a fixed number you can enter. Worst Case mode uses the impedance magnitude Z = √(R² + X²), which is the maximum value R·cosφ + X·sinφ can take at any power factor, so the reported rise bounds every PF the inverter could be commanded to. Turn it off and enter a power factor only when the inverter is locked to a known fixed PF by the DNSP connection agreement.

Does AS/NZS 4777.1 require a combined voltage drop and voltage rise check?

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.

What cable size do I need for a 5 kW single-phase solar inverter to satisfy the 2% voltage rise limit?

A 5 kW single-phase inverter exports about 21.7 A continuous at 230 V, and the 2% limit gives it a 4.6 V budget for the whole path. For copper multicore cable with 90 °C insulation (V-90 or X-90) at worst-case impedance, 4 mm² covers roughly 17 m of total path, 6 mm² about 26 m, 10 mm² about 45 m and 16 mm² about 71 m. In 75 °C V-75 the same sizes reach about 18 m, 28 m, 47 m and 75 m. Those lengths are the whole run added together (inverter cable plus any submain plus the consumer mains), not per segment. The ElecAS calculator returns the actual smallest standard size after applying the AS/NZS 3008.1.1:2025 impedance values and the AS/NZS 4777.1 2% limit to your specific install.

Does cable temperature affect voltage rise?

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.

Can I use aluminium cable for solar inverter AC connections?

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 the calculator restricts it to the 75 °C and 90 °C insulation classes (V-75, X-90, R-90) because 110 °C aluminium is not manufactured in Australia. Aluminium sizes also start at 16 mm². Always confirm aluminium-rated terminations on the inverter, isolator and switchboard: many smaller residential inverters specify copper-only terminations.

ElecAS

Voltage Rise Calculator: AS/NZS 4777.1 Solar PV & Inverter Compliance for Australia

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 (consumer mains, submains and each inverter's own final subcircuit) 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 sharing the mains and submains with an independent cable run per inverter, worst-case impedance evaluation, export-limited systems, copper and aluminium conductors, 75 °C PVC (V-75), 90 °C XLPE (X-90) and elastomeric (R-90) and 110 °C XLPE and elastomeric (X-HF-110, R-HF-110) insulation, multi-core and single-core arrangements, and the 1–630 mm² cable size range wherever AS/NZS 3008.1.1 publishes an impedance row for the chosen arrangement. 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.

Check solar inverter voltage rise against the AS/NZS 4777.1 2% limit. Enter the inverters, the cables and the run lengths, and this voltage rise calculator works the whole path from the inverter a.c. terminals back to the point of supply using AS/NZS 3008.1.1:2025 impedances, then tells you whether it passes and which cable to upsize if it does not.

Voltage rise at a glance: the AS/NZS 4777.1 2% limit

AS/NZS 4777.1 Clause 3.3.3 caps voltage rise at 2% of nominal from the point of supply to the inverter a.c. terminals.
The 2% limit is about 4.6 V on a 230 V single-phase supply and 8 V line-to-line on 400 V three-phase.
Voltage rise is evaluated at the rated current of the inverter energy system at full export.
Rise is the mirror image of voltage drop and uses the same AS/NZS 3008.1.1 conductor impedances.

Who this voltage rise calculator 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 this voltage rise calculator applies

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)

What this voltage rise calculator does

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 (consumer mains, submains and each inverter's final subcircuit), with the connection point set either to MSB direct (POS → MSB → inverter) or via a distribution board (POS → MSB → DB → inverter), which fixes exactly which cable segments carry the export current.
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 (standard and flexible) and aluminium conductors, 75 °C PVC (V-75), 90 °C XLPE (X-90) and elastomeric (R-90), and 110 °C XLPE and elastomeric (X-HF-110, R-HF-110) insulation, across the 1 mm² to 630 mm² size range: the size list is filtered to the sizes AS/NZS 3008.1.1:2025 actually publishes for the chosen conductor and arrangement, so a size with no impedance row is never offered.
Cable arrangement selector (multicore circular, multicore shaped, and single-core in trefoil, flat touching or spaced formation) chooses the AS/NZS 3008.1.1 impedance row that matches the real install, so the reactance used in the rise reflects how the cores are actually run.
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 a hard export limit is configured the calculator applies the limited current to the consumer mains (the only segment beyond the export-limit measurement point), 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 calculate voltage rise for a solar PV inverter under AS/NZS 4777.1

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.
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.
Set the connection point: Choose MSB direct, where the inverters connect at the main switchboard and the path is POS → MSB → inverter, or Via DB, where they connect at a downstream distribution board and the path is POS → MSB → DB → inverter. This fixes the sequence of cable segments the inverter current flows through back to the point of supply.
Enter each cable segment: For the consumer mains, the submains (when connecting via a DB) and each inverter's final subcircuit, enter cable size (mm²), conductor (copper, flexible copper or aluminium), insulation (V-75, X-90, R-90, X-110 or R-110) and length in metres. The calculator pulls R and X per kilometre from the AS/NZS 3008.1.1:2025 impedance tables at the insulation operating temperature.
Pick the cable arrangement: Select the arrangement that matches the physical install: multicore circular, multicore shaped, or single-core in trefoil, flat touching or spaced formation. The arrangement controls which impedance row the tool reads, and therefore the reactance used in the rise.
Set power factor and worst-case mode: Leave Worst Case on so the tool uses the full impedance magnitude Z = √(R² + X²): the largest value R·cosφ + X·sinφ can take at any power factor. Untick it and enter a power factor only when the inverter is configured to operate at a known fixed PF.
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 applies the limited current to the consumer mains (not nameplate), so the rise on the shared upstream cable reflects the real continuous export.
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.
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.

What the 2% voltage rise limit means in volts

The 2% is a percentage of the nominal voltage at the point of supply, so it converts to a fixed number of volts before you calculate anything. On a 230 V single-phase supply, 2% is 4.6 V. On a 400 V three-phase supply, 2% is 8 V line-to-line, which is the same 4.6 V measured line-to-neutral. That figure is the entire budget for every cable between the inverter a.c. terminals and the point of supply added together, not per cable.

What that budget buys in metres depends on the current and the conductor. The table below is the maximum total inverter-path length that stays inside the 2% limit, taken straight from the same AS/NZS 3008.1.1:2025 impedance tables and worst-case impedance the calculator uses, for copper multicore cable with 90 °C insulation (V-90 or X-90, the usual solar a.c. cable). Cable in 75 °C V-75 runs a little cooler and buys roughly 5% more length. Treat these as a sizing sanity check, not a substitute for running the real path: a real installation splits the budget across the inverter cable, any submain and the consumer mains.

Maximum total inverter-path length at the AS/NZS 4777.1 2% voltage rise limit (copper, multicore, 90 °C insulation, worst-case impedance)
Cable size	5 kW single-phase (21.7 A)	10 kW single-phase (43.5 A)	10 kW three-phase (14.4 A)	30 kW three-phase (43.3 A)
4 mm²	17 m	8 m	54 m	18 m
6 mm²	26 m	13 m	81 m	27 m
10 mm²	45 m	22 m	137 m	45 m
16 mm²	71 m	35 m	217 m	72 m
25 mm²	113 m	56 m	343 m	114 m
35 mm²	157 m	78 m	475 m	158 m

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. On MSB direct the path is the consumer mains plus each inverter's own final subcircuit back to the main switchboard. Via DB adds the submain between the MSB and the distribution board, so the path becomes mains plus submain plus each inverter's final subcircuit. The current in each segment is the inverter export current at that point: each inverter's own final subcircuit carries only its own current, while the shared submain and consumer mains carry the aggregated current of every inverter.

Single-phase vs three-phase behaviour

Both cases use the AS/NZS 3008.1.1 route form ΔU = K × I × Z × L, where K accounts for the return path, I is the rated current of the IES in amperes (per Clause 3.3.3), Z is the effective impedance per metre and L is the route length in metres. For a single-phase inverter K = 2 (active plus neutral), so ΔU = 2 × I × (R·cosφ + X·sinφ) × L, where R and X are the AS/NZS 3008.1.1 resistance and reactance 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 K = √3, so 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 produce roughly one-third the per-phase current of a single-phase inverter of the same kW rating, so on the same cable run the rise in volts is around 30% of the single-phase figure and (because it is expressed against 400 V rather than 230 V) the percentage rise is closer to one-sixth. That 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.

Because the inverter's operating PF moves with terminal voltage, the calculator's Worst Case mode does not pick a single PF. It uses the full impedance magnitude Z = √(R² + X²), which is mathematically the largest value R·cosφ + X·sinφ can take at any power factor: so the reported rise bounds every PF the inverter could be commanded to. Turning Worst Case off lets you enter a fixed power factor and evaluates Z = R·cosφ + X·sinφ at that PF, which is appropriate only when the inverter is locked to a known PF by the connection agreement.

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: reconnecting the inverters at the main switchboard instead of a downstream distribution board (MSB direct rather than Via DB) removes the submain 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 consumer mains (the segment beyond the export-limit measurement point), while the submain and each inverter's own cable stay on full rated current; otherwise leave it off and size everything on the full IES rated current.

For multi-inverter installations the rise on each shared segment uses the sum of the currents of every inverter. Two 5 kW single-phase inverters on the same distribution board both contribute their 21.7 A to the submain and the consumer mains, but each carries only its own 21.7 A on its own final subcircuit. The tool aggregates the shared segments automatically and reports the pass/fail against the worst inverter path.

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.

Voltage rise terminology

Voltage rise: The increase in voltage at the inverter terminals above the point-of-supply voltage when the inverter exports power, caused by current flowing back through the cable impedance.
Point of supply: The boundary between the distribution network and the installation, from which the AS/NZS 4777.1 voltage rise path to the inverter terminals is measured.
Export limit: A hard cap on the power an inverter system may export to the grid. It reduces the current, and therefore the voltage rise, in the shared consumer mains.
253 V ceiling: The +10% steady-state upper limit on a 230 V supply. Grid voltage near this ceiling plus cable voltage rise pushes the inverter toward its AS/NZS 4777.2 over-voltage response.

Reviewed by

Wisam Tozah: Associate Electrical Engineer. B.Eng (Electrical), MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE(Aus). See how these calculations are verified. LinkedIn.

Voltage rise questions, answered

What is the AS/NZS 4777.1 voltage rise limit for solar inverters in Australia?: 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.
How is voltage rise calculated for a grid-connected solar PV inverter?: Per AC cable segment ΔU = K × I × (R·cosφ + X·sinφ) × L, where K = 2 for single-phase (active plus neutral return) and K = √3 for balanced three-phase, 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 at the insulation operating temperature, L is the cable route length in metres, and φ is the inverter operating power factor angle. At worst case the bracket is replaced by the impedance magnitude √(R² + X²). 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.
Does the 2% AS/NZS 4777.1 voltage rise limit include the consumer mains?: 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.
How do I reduce voltage rise on a solar PV installation that fails the 2% limit?: 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.
Does an export-limited inverter still have to satisfy the 2% voltage rise limit?: 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 consumer mains only: the one segment beyond the export-limit measurement point, with the submains and each inverter cable still assessed at full output; otherwise size on the full IES rated current.
How does the calculator handle multiple inverters on the same installation?: Add each inverter with its own size, name and AC cable run; the connection point (MSB direct or via a DB) is set once for the installation and is shared by every inverter. The tool aggregates currents per segment: the consumer mains and, where used, the submain carry the sum of all inverters, while each inverter's own final subcircuit carries only its own current. The final pass/fail verdict checks the worst-case inverter path against the 2% AS/NZS 4777.1 limit.
What is the difference between voltage drop and voltage rise?: 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, which sets a 5% limit from the point of supply to any point in the installation (a note to that clause allows more where supply comes from a substation forming part of the installation). 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.
Should I use worst-case power factor for AS/NZS 4777.1 voltage rise?: Yes, wherever the inverter is configured for any AS/NZS 4777.2 reactive response mode (volt-var, fixed PF other than unity, PF response), because the operating PF then moves with terminal voltage and is not a fixed number you can enter. Worst Case mode uses the impedance magnitude Z = √(R² + X²), which is the maximum value R·cosφ + X·sinφ can take at any power factor, so the reported rise bounds every PF the inverter could be commanded to. Turn it off and enter a power factor only when the inverter is locked to a known fixed PF by the DNSP connection agreement.
Does AS/NZS 4777.1 require a combined voltage drop and voltage rise check?: 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.
What cable size do I need for a 5 kW single-phase solar inverter to satisfy the 2% voltage rise limit?: A 5 kW single-phase inverter exports about 21.7 A continuous at 230 V, and the 2% limit gives it a 4.6 V budget for the whole path. For copper multicore cable with 90 °C insulation (V-90 or X-90) at worst-case impedance, 4 mm² covers roughly 17 m of total path, 6 mm² about 26 m, 10 mm² about 45 m and 16 mm² about 71 m. In 75 °C V-75 the same sizes reach about 18 m, 28 m, 47 m and 75 m. Those lengths are the whole run added together (inverter cable plus any submain plus the consumer mains), not per segment. The ElecAS calculator returns the actual smallest standard size after applying the AS/NZS 3008.1.1:2025 impedance values and the AS/NZS 4777.1 2% limit to your specific install.
Does cable temperature affect voltage rise?: 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.
Can I use aluminium cable for solar inverter AC connections?: 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 the calculator restricts it to the 75 °C and 90 °C insulation classes (V-75, X-90, R-90) because 110 °C aluminium is not manufactured in Australia. Aluminium sizes also start at 16 mm². Always confirm aluminium-rated terminations on the inverter, isolator and switchboard: many smaller residential inverters specify copper-only terminations.