A solar system’s size is usually its panel capacity in kilowatts (kW), while a battery is described by its storage capacity in kilowatt-hours (kWh). The right size depends on your electricity use, when you use power, roof space, budget, local network export limits and whether you plan to add a battery or an electric vehicle. A larger system can generate more energy, but may not be the best-value choice if much of its output is exported at a lower feed-in tariff. Review your bills and ask an accredited installer to model suitable options for your home.