A solar battery stores excess electricity from your panels for use at night or during periods of low solar generation. Compare usable capacity, power output, round-trip efficiency, warranty terms, expected lifespan and whether the system can provide backup during a blackout. The right size depends on your household’s electricity use, solar production, tariff and export arrangements, so a larger battery is not automatically better value. Get quotes from appropriately licensed installers and check current guidance from the Clean Energy Council and your electricity retailer before deciding.