What size solar system do I need?
There is no single system size that suits every household. Start with electricity use, then check the roof, inverter and future loads together.
On this page
Understand kW and kWh first · Look at when you use electricity · Check roof layout and inverter selection · Compare the proposed outcome · Your solar sizing checklist
Understand kW and kWh first
Kilowatts (kW) describe power; kilowatt-hours (kWh) describe energy used or generated over time. A panel array’s advertised kW rating is not a promise that it will produce that amount continuously.
For example, fifteen 440 W panels have a combined nameplate rating of 6.6 kW: 15 × 440 ÷ 1000. This arithmetic describes array size, not daily generation, savings or suitability for your roof.
Look at when you use electricity
Gather daytime and evening usage information rather than choosing from a bill’s dollar total alone. List loads you can schedule during the day and those that need to run after sunset.
Ask the proposal to state the usage assumptions behind its recommended size. If an EV or electric hot-water system is planned, request a separate scenario rather than treating future consumption as certain.
Check roof layout and inverter selection
Roof space, orientation and shading are part of solar system design. The Australian Government’s sizing guide explains why the roof and equipment specifications can constrain the options.
Request a layout showing panel positions and an equipment schedule with the exact inverter. Panel-array capacity and inverter output are separate specifications; ask the designer to explain the proposed combination and relevant connection constraints.
Compare the proposed outcome
Ask for estimated generation assumptions, installation inclusions and what would change the recommended size. Compare proposals using the same usage information so differences are easier to understand.
A larger nameplate number is not enough to compare two offers. Check the actual module model, available monitoring, installation scope, equipment warranty documents and support arrangements. Keep numerical forecasts separate from guarantees.
Your solar sizing checklist
Before enquiring, collect your recent bill, typical daytime occupancy, any interval data, planned appliances and photographs of existing equipment. You do not need to choose the exact panel count yourself.
During the consultation, ask: Why this array size? Why this inverter? What assumptions drive the forecast? What changes if I add a battery or EV later? Record those answers with the quote.
Your next step
Explore panel options, then ask Solar4life for a design matched to your usage and property.
Sources and further reading
Australian Government — size your solar system ↗
General buying guidance. Equipment selection and installation requirements depend on your property and the proposed system.