What size solar battery do I need?
Most UK homes suit a solar battery of 5 to 10 kWh, while larger homes or those with an EV often go for 10 to 13 kWh. The right size matches your daily solar surplus and your evening electricity use. Oversizing wastes money on capacity you cannot fill or empty each day.
Battery size by home
| Home | System | Battery |
|---|---|---|
| Smaller home | 3 to 4 kWp | 5 to 7 kWh |
| 3 to 4-bed home | 5 kWp | 7 to 9.5 kWh |
| Larger or EV home | 6 to 7 kWp | 9.5 to 13 kWh |
How to size it
Look at your evening and overnight electricity use, and how much surplus your panels make on an average day. A battery you can fill from solar and largely empty each evening is the sweet spot. Going much bigger rarely pays unless you are also charging it cheaply overnight to cover an EV or heat pump.
Frequently asked questions
- Is a bigger battery always better?
- No. A battery larger than your daily surplus and evening use sits part-empty, so the extra capacity does not earn its cost.
- Can I add more battery capacity later?
- Many modern batteries are modular, so you can expand capacity later if your needs grow, such as after getting an EV.
Related questions
Indicative estimates based on UK average data. Last updated 27 May 2026.