Solar calculator

Size your solar around your life.

Start with the electricity you actually use and what you spend. Use an average of recent bills, ideally across 12 months, to account for seasonal changes.

Your electricity usage

Use consumption and spend from the same billing period. One electricity unit is one kWh.

Monthly electricity consumption (kWh)Find total units used on your bill or prepaid meter history. Enter consumption, not the meter reading.

Monthly electricity spend (R)Electricity charges only, including fixed electricity charges. Exclude water, rates, arrears and once-off fees.

Fixed electricity charges (R)Service, network and other charges that remain payable after installing solar.

Days in this billing periodMatch the period used for consumption and spend above.

Electricity to offset with solar: 80%Your target share of electricity consumption replaced by solar.

Adjust solar assumptions

These are editable planning assumptions, not measured conditions at your property.

Peak sun hours per dayIllustrative default: 5. Use a location-specific solar assessment for your roof.

System performance (%)Illustrative default: 75%, allowing for heat, conversion, wiring and other losses.

Solar generation used on site (%)Illustrative default: 80%. Daytime demand and battery storage affect how much generation you can use.

Your system starting point

Enter your monthly kWh and spend to see an estimate. Values must be valid and fixed charges cannot exceed your spend.

What about the inverter and battery?

Monthly kWh sizes the energy requirement. Inverter sizing also needs your simultaneous appliance load and starting surges. Battery sizing needs the essential loads and backup hours you want. Our site assessment checks these, roof space, shading and seasonal solar output before confirming a system.

Discuss my system with NOVA-X

Method background: PV performance modelling. This calculator is a simplified estimate and does not run PVWatts.