Solar system size is measured in kilowatts (kW), while your electricity use is measured in kilowatt-hours (kWh). A suitable size depends on your household’s daytime energy use, roof space and orientation, budget, future plans, and your distributor’s export limits—not simply the number of bedrooms. Check recent electricity bills and consider whether you want to add a battery, an electric vehicle or more daytime appliances. A Clean Energy Council-accredited installer can assess your site and explain expected generation, while energy.gov.au provides general Australian solar guidance.