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AmpSize

Floor area demand calculator

Estimate commercial demand from floor area and use.

AS/NZS 3000 Table C3

Reads AS/NZS 3000:2018. Tables checked 1 Oct 2026.

Try a job 4

Each job fills in example values. Replace them with your values.

Inputs

Worked example with the default inputs. The live calculator replaces it when the page loads.

Phases
Three phase
Phase voltage
230 V
Figure from the table
Printed average
Areas
2 rows
Special equipment
0 kVA

Maximum demand per phase

217.39A

Total demand
150kVA
Offices · Light and power
75kVA
Offices · Airconditioning, zonal reheat
75kVA

This result is a design aid. Verify it against the current standard.

Calculation steps

  1. Figure taken from Table C3Printed average

    AS/NZS 3000:2018 Table C3

  2. Offices · Light and power, energy demand50VA/m²

    AS/NZS 3000:2018 Table C3

  3. Offices · Light and power, 1500 m²75kVA

    AS/NZS 3000:2018 Table C3

  4. Offices · Airconditioning, zonal reheat, energy demand50VA/m²

    AS/NZS 3000:2018 Table C3

  5. Offices · Airconditioning, zonal reheat, 1500 m²75kVA

    AS/NZS 3000:2018 Table C3

  6. Total demand150kVA

    AS/NZS 3000:2018 App C Para C2.4.3

  7. Current per phase, kVA ÷ (3 × phase voltage)Result217.39A

    AS/NZS 3000:2018 App C Para C2.4.3

About this calculator

How this is calculated

The tool estimates the maximum demand of a commercial or light-industrial building from its floor area. It uses the energy demand method in AS/NZS 3000:2018 App C Para C2.4.3. It reads the VA per square metre from Table C3.

  1. Pick the figure. For each area, choose an occupancy and a use. The tool takes the printed average, or the low or high end of the printed range (Table C3). You can type your own figure instead.
  2. Work out each area. The tool multiplies the area by the VA per square metre and divides by 1000. The result is kVA.
  3. Add EV charging. The NOTE to Table C3 puts EV charging on top of all other energy demands. The tool adds the carpark EV rows to the total.
  4. Add special equipment. Table C3 prints no figure for it. You enter its kVA from the load details, and the tool adds it.
  5. Total demand. The tool adds every area and the special equipment (Para C2.4.3).
  6. Current. On one phase, the tool divides the kVA by the phase voltage. On three phases, it divides by 3 times the phase voltage. That gives the current in each phase.
StepTable or clauseWhat it decides
Figure per areaTable C3The VA per square metre for each use
EV chargingNOTE to Table C3The charging load added on top
Total demandApp C Para C2.4.3The sum of the areas and special equipment
CurrentApp C Para C2.4.3The demand in amps on each phase

Worked example

  • Small retail and office building with basement EV charging. Shops of 600 m² at 70 VA/m² for light and power and 30 VA/m² for air conditioning. Offices of 400 m² at 50 and 25 VA/m². A basement carpark of 300 m² at 15 VA/m², plus its EV charging at 20 VA/m². The total demand is 100.5 kVA. The current is 145.65 A per phase at 230 V.
  • The Paragraph C2.4.3.2 case. 1500 m² of office at 50 + 50 VA/m². The total demand is 150 kVA. The current is 217.39 A per phase.

Limits

  • Table C3 is for commercial and light-industrial buildings. It is not for homes. Use Table C1 for a home.
  • The figures depend on the climate, the hours of use, energy management and how evenly the load spreads.
  • The per phase figure assumes an even spread over three phases. Check the heaviest phase where the load is uneven.
  • The tool uses the phase voltage. On a 230/400 V supply, enter 230.
  • Special equipment has no printed figure. You must know its kVA. The tool does not guess it.
  • An own figure outside the printed range gives a warning. Check it before you rely on it.
  • To work from a list of loads, use the Table C2 method in the Maximum Demand tool.

See also: The energy demand method and Table C3, Shop and office maximum demand by floor area and the Maximum Demand tool.

Questions

Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.

When do I use Table C3 instead of Table C2?

Table C3 suits a commercial or light-industrial building at the early design stage, when you know the floor area and the use but not the loads. Table C2 needs the load groups. Once the loads are known, check the demand by Table C2.

Which figure should I take from the range?

The tool opens on the printed average. The standard says the figures depend on the climate, the hours, energy management and how evenly the load is spread. Take the high end for a hot climate or long hours, or enter your own figure.

How does the tool turn kVA into amps?

It divides the total VA by the phase voltage. On three phases it divides by three times the phase voltage, so 150 kVA at 230 V gives 217.39 A per phase. That matches the example in Paragraph C2.4.3.2.

Is EV charging in the carpark figure?

No. Table C3 lists EV charging as its own row under open air and basement carparks, and its NOTE puts it in addition to all other demand. Add an EV charging area beside the carpark area.

What about special equipment in a warehouse or workshop?

Table C3 prints no figure for special equipment. Work it out from the load details and enter it in kVA. The tool adds it to the total.

Clauses and tables this tool reads

Every clause and table, with how each was verified

Tables last checked on 1 Oct 2026.

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