Question 1

How does AS/NZS 3000 require maximum demand to be calculated?

Accepted Answer

AS/NZS 3000:2018 Appendix C provides standardised diversity tables for calculating maximum demand. Table C1 covers single-domestic and multi-domestic installations; Table C2 covers commercial and industrial. Each load type (lighting, power points, water heating, motors, EV chargers) is assigned a per-circuit kW value or a percentage diversity factor, and the sum gives the maximum demand in kVA or amps. The calculator implements both tables and selects the right one based on your installation type.

Question 2

When do I use Table C1 versus Table C2?

Accepted Answer

Table C1 applies to single-domestic dwellings (one home) and multi-domestic dwellings (apartments, units). Table C2 applies to all other installation types: commercial, retail, industrial, hospitality. If your installation mixes residential and commercial use, for example a shop with a flat above, calculate each part separately and add them. The calculator handles both tables and the dual-use combination.

Question 3

How do diversity factors work for residential lighting and power circuits?

Accepted Answer

Under Table C1 the first lighting circuit counts at 1000 W and each additional lighting circuit at 750 W (placeholder pending CPEng validation). Power point circuits start at 1000 W for the first and 500 W per additional circuit. The diminishing values reflect that not every circuit is loaded simultaneously. Add larger appliances (cooking, water heating, heating, EV) per their own table entry rather than rolling them into the lighting or power totals.

Question 4

How is maximum demand for an EV charger calculated?

Accepted Answer

EV chargers are treated as a continuous load at 100 percent of their rated current with no diversity. A 32 A single-phase EV charger contributes about 7.4 kW; a 22 kW three-phase charger contributes 22 kW. Some supply authorities additionally require load management or controlled charging for installations with multiple chargers or limited supply capacity. The calculator includes EV charger as a dedicated load class.

Question 5

How does maximum demand select the main switch rating?

Accepted Answer

The main switch must be rated at least equal to the calculated maximum demand current. Convert kVA to amps using the supply voltage: divide kVA by 0.230 for single-phase, or by (1.732 times 0.400) for three-phase. Pick the next standard rating from 40, 63, 80, 100, 125, 160, 200, 250, 315, 400, or 630 A. The calculator does this automatically.

Category	Raw (kW)	Diversity	After (kW)
Lighting	3.00	0.83	2.50
Power Point Circuits	4.00	0.63	2.50
Heating/Cooling	0.00	1.00	0.00
Cooking Appliances	6.00	1.00	6.00
Water Heater	3.60	1.00	3.60
Other Fixed Appliances	0.00	1.00	0.00
Motors	0.00	1.00	0.00
Total			14.60

Maximum Demand Calculator

Inputs

Lighting & Power

Heating & Cooling

Cooking Appliances

Water Heating

Results

Maximum Demand for AS/NZS 3000:2018

Residential maximum demand (Table C1)

Commercial maximum demand (Table C2)

Main switch selection

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