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Maximum Demand Calculator

AS/NZS 3000:2018 Appendix C maximum demand for domestic and non-domestic installations

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Installation

Table C1

Converts kW and W ratings to amps

L1, L2 and L3

Load Configuration

1 / 5 loads
1
0.0 A on L1
0.0 A on L2
0.0 A on L3

Result

Add a load to see the maximum demand.

New to it? Read the step-by-step maximum demand guide.

How it's calculated

The Appendix C method

Each load is assigned to a load group of the table for the installation type, the group's diversity rule turns its connected load into amps, and the groups are added per phase.

Connected load to current

rating, W
230 V line-to-neutral (400 V for a line-to-line load)

Demand of a load group

For example Table C1 (a)(i) lighting: 3 A for 1 to 20 points plus 2 A per extra 20; (c) a range: 50% of the connected load; (d) air conditioning: 75%; (f) storage water heaters: full load.

Maximum demand per phase

The heaviest loaded phase is the maximum demand used to size the consumer mains and the main switch.

Floor-area method (Table C3)

For non-domestic installations assessed before the loads are known.

Standards referenced

  • AS/NZS 3000:2018 Clause 2.2.2 (maximum demand)
  • AS/NZS 3000:2018 Appendix C, Table C1 (domestic), Table C2 (non-domestic) and Table C3 (floor area)

Worked example: a single-phase house

A single domestic electrical installation at 230 V, single phase, assessed with Table C1, column 2.

  1. 1. 30 lighting points
  2. 2. 40 × 10 A socket-outlet points
  3. 3. 10 kW range
  4. 4. 7.2 kW split system air conditioner
  5. 5. 3.6 kW storage water heater

The maximum demand is 80.9 A on the one phase: each load group's rule already applies its diversity, so the groups simply add. Size the consumer mains and main switch for at least 81 A.

Frequently Asked Questions

Maximum Demand Questions Answered

What is maximum demand?

Maximum demand is the largest current an installation is expected to draw at one time. AS/NZS 3000:2018 Appendix C applies diversity to the connected loads, because not everything runs at full load together, and the result sizes the consumer mains, submains and main switch.

Which Appendix C table should I use?

Table C1 covers single domestic dwellings and blocks of living units. Table C2 covers non-domestic installations such as shops, offices, factories, schools and hotels. Table C3 assesses non-domestic installations from floor area. Choose the installation type and the calculator picks the table.

Does maximum demand decide the cable size?

It gives the design current. The cable still has to carry that current after derating and stay within the voltage drop limit, which the cable size calculator checks to AS/NZS 3008.1.1:2025.

Is the maximum demand calculator free?

Yes. Anyone can run it with up to 5 loads without an account. A free account saves calculations to a project and downloads the AS/NZS 3000:2018 report; a subscription removes the load limit.

Reviewed by Ahmed Tayeh, electrical engineer at CableHero. The calculator is a design aid: the designer remains responsible for checking the installation against the standards.

Guides

Learn the method

How to use this calculator

Add the loads, let Appendix C apply the diversity, and read the demand on each phase.

Read the guide: How to use the maximum demand calculator

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