A battery is usually measured in kilowatt-hours (kWh). A larger battery stores more power, but only saves money if you use that power.
A simple way to start:
- Look at your electricity bill or smart meter data for typical evening use.
- Decide how much of that evening use you want to cover from the battery.
- Match the battery to that figure, then check the inverter size.
Common sizes for UK homes start at about 5kWh and go up to around 16kWh for larger households. At Solar Heaven we recommend a size from your bills, not from a sales target, and we offer several options so you can compare.
Published October 25, 2026 · All guides