A solar battery stores surplus electricity generated during the day so you can use more of your solar power at night or during a blackout, if the system supports backup. Choosing the right size depends on your household’s electricity use, solar system, roof generation and whether you want backup power. A battery may reduce electricity purchases, but its value depends on installation costs, energy prices, usage patterns, warranty and expected lifespan. Ask an accredited installer for a site-specific assessment and check current battery incentives through the official energy.gov.au website.