When should I use Table C3 instead of itemising loads?

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.

Does Table C3 give a higher or lower demand than C2?

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.

Can Table C3 be used as the final design demand?

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.

When can I use the AS/NZS 3000 Table C3 energy method?

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.

How much historical data do I need for Table C3?

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.

Can the Table C3 result be higher than the Table C1 / C2 result?

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.

Does Table C3 still require the Clause 2.2.2 minimum current floor?

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.

ElecAS

Table C3 Energy Demand Calculator

Calculate non-domestic energy demand using floor-area and occupancy inputs aligned with AS/NZS 3000 Table C3.

Why this page matters

Calculate non-domestic energy demand using floor-area and occupancy inputs aligned with AS/NZS 3000 Table C3. This static content is published so the canonical route has meaningful crawlable HTML even before the interactive application hydrates.

Who this page is for

Designers estimating demand from floor area and occupancy when the energy-demand method is the better fit.

Relevant standards

AS/NZS 3000 Table C3

What this tool helps with

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 calculate maximum demand using the AS/NZS 3000 Table C3 energy method

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).
Identify the historical peak kW — Pick the highest recorded 30-minute kW value across the 12-month period. This is the historical peak.
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.
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.
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.
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.

Reviewed by

Wisam Tozah — Associate Electrical Engineer. B.Eng (Electrical), MIEAust, CPEng, NER, NSW DBP, NSW PRE, APEC, IntPE(Aus). LinkedIn.

Frequently asked questions

When should I use Table C3 instead of itemising loads?: 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.
Does Table C3 give a higher or lower demand than C2?: 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.
Can Table C3 be used as the final design demand?: 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.
When can I use the AS/NZS 3000 Table C3 energy method?: 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.
How much historical data do I need for Table C3?: 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.
Can the Table C3 result be higher than the Table C1 / C2 result?: 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.
Does Table C3 still require the Clause 2.2.2 minimum current floor?: 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.