Free Electrical Tool
Maximum Demand Calculator
Estimate the maximum electrical demand for a house, granny flat, commercial or industrial property using the demand factors based on AS/NZS 3000 Appendix C — an indicative estimate of the figure electricians use to size consumer mains, switchboards and supply upgrades.
How maximum demand is calculated in NSW
Maximum demand is the backbone of every consumer mains sizing, switchboard upgrade, granny flat connection and commercial fit-out. AS/NZS 3000 Appendix C sets out demand factors for domestic installations (Table C1 for single dwellings, Table C2 for multiple units), while commercial and industrial installations are assessed by calculation, comparison with a similar installation, or measurement.
Ducted air conditioning, EV chargers, pool heat pumps and electric cooking are the loads that most often tip a Sydney home past its existing 63A supply. For commercial and industrial sites — factories, warehouses, cafes, medical suites — motor loads and HVAC dominate, and the distributor will ask for a documented maximum demand with any consumer mains or switchboard upgrade application.
As Level 2 ASP electricians accredited on the Ausgrid, Endeavour Energy and Essential Energy networks, Sydney Power Group prepares certified maximum demand assessments and completes the upgrade work end-to-end — consumer mains, metering, and network paperwork included. Also try our voltage drop calculator.
Maximum demand FAQs
What is maximum demand in electrical terms?
Maximum demand is the highest electrical load an installation is expected to draw at any one time, measured in amps. It determines the size of your consumer mains, main switch and supply. In NSW it is assessed using AS/NZS 3000 Appendix C or by calculation/measurement for larger commercial and industrial installations.
How do I calculate maximum demand for a house in NSW?
For a single domestic dwelling, AS/NZS 3000 Table C1 applies demand factors to each load group: lighting, power points, cooking appliances, air conditioning, hot water, pools and EV chargers. Each group contributes a diversified current, and the total is the maximum demand used to size the consumer mains.
How is maximum demand calculated for commercial and industrial buildings?
Commercial and industrial maximum demand is usually determined by calculation (applying diversity factors to the connected load of each load group), by assessment against a similar installation, or by measurement over time. Larger sites with three-phase supplies, motor loads or CT metering generally need a documented assessment by a licensed electrician or Level 2 ASP.
Why does maximum demand matter when upgrading a switchboard or consumer mains?
Your consumer mains, main switch and service protection must be rated for the installation's maximum demand. Adding ducted air conditioning, an EV charger, a pool or a granny flat can push demand past the existing supply capacity — which is when an upgrade from 63A to 80A/100A, or from single-phase to three-phase, is required.
Is this calculator a substitute for a certified maximum demand assessment?
No. This tool provides a guide based on the standard demand factors in AS/NZS 3000 Appendix C. Network providers (Ausgrid, Endeavour Energy, Essential Energy) and certifiers require a maximum demand assessment prepared by a licensed electrician. Sydney Power Group can prepare and certify this as part of any Level 2 works.