Maximum demand calculator
Estimate maximum demand for domestic or non-domestic loads.
Reads AS/NZS 3000:2018 and Electricity (Safety) Regulations 2010. Tables checked 19 Sept 2026.
Try a job 8
Each job fills in example values. Replace them with your values.
- Size a house mainThe maximum demand of a house with a heat pump, from Table C1.
- Work out commercial maximum demandThe maximum demand of a tenancy from Table C2.
- Work out demand for a block of unitsThe demand of twelve units, four on each phase.
- Work out demand with spa and floor heatingThe demand of a house with heating and a spa pool.
- Work out demand for a caféThe demand of a café with cooking and refrigeration.
- Work out demand for a small factoryThe demand of a workshop with lighting, sockets and motors.
- Work out demand for a three-phase houseThe demand per phase of a large house.
- Work out demand for an office floorThe demand of a 400 m² office with air-conditioning.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Demand table
- Table C1 · domestic
- Installation
- Single domestic or one living unit
- Phases
- Single phase
- Phase voltage
- 230 V
- Load groups
- 4 rows
Maximum demand
50.43A
- Per phase
- 50.43A
- A(i) · Lighting
- 5A
- B(i) · Socket-outlets and permanently connected equipment up to 10 A
- 15A
- C · Ranges, cooking appliances and laundry equipment
- 17.39A
- F · Storage water heaters
- 13.04A
This result is a design aid. Verify it against the current standard.
Calculation steps
- Demand tableC1 · single domestic
AS/NZS 3000:2018 Table C1
- A(i) · Lighting5A
AS/NZS 3000:2018 Table C1
- B(i) · Socket-outlets and permanently connected equipment up to 10 A15A
AS/NZS 3000:2018 Table C1
- C · Ranges, cooking appliances and laundry equipment17.39A
AS/NZS 3000:2018 Table C1
- F · Storage water heaters13.04A
AS/NZS 3000:2018 Table C1
- Maximum demand50.43A
AS/NZS 3000:2018 Table C1
- Maximum demand per phaseResult50.43A
AS/NZS 3000:2018 Table C1
About this calculator
How this is calculated
The tool works out the maximum demand of an installation from its loads. It follows the load group method of AS/NZS 3000 Appendix C.
- Table. Table C1 covers domestic installations: one house or living unit, or a block of living units. Table C2 covers other installations. For Table C2 you pick the occupancy.
- Load groups. You enter each load in its group, such as lighting points, socket-outlet points or kW of cooking. The tool lists only the groups the table assesses for your choice.
- Group demand. Each group has its own rule for its load. The tool applies that rule and gives the group demand in amperes. It converts each kW load at the phase voltage you enter.
- Living units per phase. A block of living units can take more than one phase. The tool then divides the units by the number of phases and rounds up. It reads the column for that number of units per phase.
- Total. The maximum demand is the sum of the group demands.
- Per phase. On three phases, the tool divides the total by three. That assumes you spread the load evenly over the phases. Where you cannot, allocate the loads per phase and check the heaviest phase.
| Step | Table or clause | What it decides |
|---|---|---|
| Domestic loads | AS/NZS 3000 Table C1 | The rule for each load group in a house or a block of living units |
| Other loads | AS/NZS 3000 Table C2 | The rule for each load group, by occupancy |
| Living units per phase | Table C1 Note 2 | The column a block of living units reads on more than one phase |
| Total and per phase | Table C1 or Table C2 | The sum of the groups and the share on each phase |
Phase voltage
Enter the phase voltage, line to neutral, such as 230 V. The tool converts every kW load at that voltage. The 400 V between lines would read every kW group 42 % low. On a three-phase supply the tool refuses a line voltage and asks for the phase voltage.
Common installations, worked with the tool
Each line states its loads. Every line uses a phase voltage of 230 V.
- House on one phase. It uses Table C1 for one house. The loads are 30 lighting points, 25 socket-outlet points, 8 kW of cooking and a 3 kW storage water heater. The maximum demand is 50.43 A.
- The same house on three phases. The maximum demand is 16.81 A per phase and 50.43 A over all phases.
- Block of 12 living units on three phases. Table C1 for blocks of living units, with the same load rows. The tool reads 4 units per phase. The maximum demand is 75 A per phase and 225 A over all phases.
- Office on three phases. It uses Table C2 for factories, shops and offices. The loads are 10 kW of lighting, 20 socket-outlets and motors of 15 A, 10 A and 5 A. The maximum demand is 44.93 A per phase and 134.78 A over all phases.
New Zealand and Australia
AS/NZS 3000 Appendix C applies in both countries, so the tool has no country select.
Keep the result
Every input sits in the page address, so the link in your browser reproduces the calculation. The PDF button prints the result with its steps and table references. Saving a calculation to a project needs a free account.
See also: Commercial maximum demand with Table C2, Domestic maximum demand with Table C1 and Maximum demand and diversity.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the maximum demand calculator do?
The tool applies the demand rule for each load group you add. It lists the demand in amperes for each group, then reports the total demand and the demand per phase. Each line shows the table and the column that produced it.
Which AS/NZS 3000 tables does the maximum demand calculator use?
It uses AS/NZS 3000:2018 Table C1 for one domestic installation or a block of living units. It uses Table C2 for other installations, with a residential or a commercial column. Choose the table and the mode first, because they change which rule each load group follows.
What decides the demand rule for each load group?
The table and the mode set the rule for every group. The supply voltage converts groups given in kilowatts into amperes. The phase count divides the total. In the living units mode, the unit count on each phase drives the result. Enter the total unit count and the phase count.
How are living units on three phases counted?
The tool divides the unit count by three, as Table C1 Note b requires. Some groups take a list of individual items, not one quantity. Some groups are by assessment and add nothing. A note appears above the regulation 59 thresholds.
Can I share or save a demand calculation?
Yes. The table, the mode, the voltage, the phases and every load row sit in the page address. Copy the link to send the same demand assessment to somebody else. Saving it under a project name needs an account. New Zealand conditions are the default.
Worked examples
- Electrical estimating calculators NZ roundupA roundup of the calculators a New Zealand estimator uses at price stage, with a Table C2 fitout worked through to a demand of 102.95 A per phase.
- AS/NZS 3000 Tables C1 and C2: demand groupsWhat the demand group letters govern, when to use Table C1 or Table C2, and a commercial assessment that returns 276.26 A total and 92.09 A per phase.
- Commercial maximum demand with Table C2A tender-stage demand assessment for a commercial building using AS/NZS 3000 Table C2, with each group demand and the per-phase figure the tool returns.
- Domestic maximum demand with Table C1Assess the maximum demand of a New Zealand house from Table C1, group by group, with a worked example that lands on 52.61 A on a single-phase supply.
Background
- IEC 60364 and the Wiring RulesIEC 60364 is the international series that AS/NZS 3000 stays aligned with. See how its parts are numbered, what TN-C-S, TT and IT mean, and where MEN fits.
- Maximum demand and diversityWhy consumer mains are smaller than the sum of the loads. The four methods of Cl 2.2.2, the Table C1 groups, and a house that lands on 70.18 A.
Clauses and tables this tool reads
- AS/NZS 3000:2018 Cl 2.2Maximum demand
- Electricity (Safety) Regulations 2010 reg 59Part 1 and Part 2 designs
- AS/NZS 3000:2018 Table C1Maximum demand, single and multiple domestic installations
- AS/NZS 3000:2018 Table C2Maximum demand, non-domestic installations
Every clause and table, with how each was verified
Tables last checked on 19 Sept 2026.
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