Without a battery, most homes use around a third of the solar energy they make. The rest is exported. A battery can push that much higher by storing the daytime surplus for the evening.Smart tariffsMany energy suppliers offer cheap overnight rates. A battery can charge then and run your home through the expensive early-evening peak.Sizing it rightBigger isn't always better. We look at your actual usage to recommend a battery that fills up and empties most days, which is where the savings come from.