Maximum Demand Calculator
AS/NZS 3000:2018 Tables C1 & C2 (Australian conditions)
Inputs
Lighting & Power
Heating & Cooling
Cooking Appliances
Water Heating
▶Other Loads
Results
Maximum Demand
Recommended Main Switch
80 A
Next standard size ≥ 63.48 A
Main Switch Rating
80 A (>= 63.47826086956522 A)
| 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 — AS/NZS 3000:2018
Maximum demand is the greatest average power drawn over a defined period, used to size main switches and determine meter/supply capacity. In Australia, maximum demand is calculated using diversity factors from AS/NZS 3000:2018 Tables C1 (residential) and C2 (commercial). Diversity factors account for the fact that not all loads operate simultaneously at full capacity.
Residential Maximum Demand (Table C1)
For residential installations, the demand calculator considers:
- Lighting circuits: First circuit = 1 kW, additional = 0.75 kW each (⚠️ PLACEHOLDER)
- Power point circuits: First = 1 kW, additional = 0.5 kW each (⚠️ PLACEHOLDER)
- Heating & Cooling: Only the larger load is at 100%, the other at 50%
- Cooking appliances: 1st = 100%, 2nd first 1 kW = 100% then 80%, 3rd+ = 60% (⚠️ PLACEHOLDER)
- Water heating: Treated as continuous load (100%)
- Fixed appliances: Each at 100%
- Motors: Largest at 100%, others at 80% (⚠️ PLACEHOLDER)
- EV charger: Treated as continuous load (100%)
Commercial Maximum Demand (Table C2)
For commercial installations, a simplified approach is used:
- Lighting: 75% diversity factor (⚠️ PLACEHOLDER)
- Socket outlets: 0.5 kW per circuit at 50% diversity (⚠️ PLACEHOLDER)
- Fixed appliances: 100%
- Motors: 85% average diversity (⚠️ PLACEHOLDER)
Main Switch Selection
The main switch rating must be ≥ the calculated maximum demand current. The calculator selects the next standard switch size (40A, 63A, 80A, 100A, 125A, 160A, 200A, 250A, 315A, 400A, 630A).
Important Notes
⚠️ Disclaimer: This calculator uses placeholder diversity factors pending CPEng verification against AS/NZS 3000:2018. For final design, these results must be verified by a qualified electrical engineer and checked against the current edition of AS/NZS 3000:2018 and the applicable electricity distributor's connection requirements.