The right solar system size depends on your household’s electricity use, when you use power, available roof space, budget and any export limits set by your electricity distributor. Review at least 12 months of bills and consider a system sized to your daytime demand, especially if you are not planning to install a battery. A qualified solar installer can assess your roof, shading, switchboard and local connection requirements before recommending a size. You can also compare likely generation with tools such as the Australian Government’s SunSPoT calculator, but actual results vary with location, orientation and weather.