Battery size optimiser examples
Compare 5 kWh and 10 kWh batteries across 2–15 kWh/day of shiftable energy. The larger battery only gains value when it can actually be used.
Size a battery around shiftable energy, not headline capacity
The range above starts with daily energy that could realistically be moved from one time of day to another. That is more useful than choosing a battery purely from annual electricity consumption. A household might use a lot of electricity overall but have little evening demand to cover, while another household with lower annual consumption may have a concentrated evening peak that a battery can serve well.
Battery capacity should also be separated from usable capacity. Reserve settings, inverter limits, efficiency losses and battery-management rules can reduce the amount available for daily shifting. Solar households should consider how often the battery can be filled from surplus generation; tariff-charging households should consider the length and price of the cheap window.
Test more than one day type
Use the optimiser with a typical weekday, a high-use day and a low-use day rather than relying on a single average. If a larger battery only adds value on a few exceptional days, the extra installed cost may take a long time to recover. The aim is a capacity that is used regularly, not simply the biggest unit that fits.