Start by checking your electricity bills to estimate daily energy use, then consider how much power you use during daylight hours. A system’s size is measured in kilowatts (kW), but the best option also depends on roof space, shading, orientation, budget, battery plans and your distributor’s export limits. Oversizing may improve daytime generation, while a smaller system could suit a lower-use home or restricted roof. A reputable accredited installer can model your usage and roof, and you should compare the proposal with guidance from the Clean Energy Council and your electricity distributor.