Battery storage can increase the amount of your solar electricity used at home, but it is not automatically the best financial choice. Size and tariff strategy matter more than simply buying the largest battery.

What a home battery does

A battery stores surplus solar generation for later use. It can also charge from the grid during cheaper tariff periods and supply the home when electricity is more expensive. This changes when you import electricity; it does not create extra energy.

How much capacity do you need?

• Your daily and evening electricity use
• The size and seasonal output of the solar array
• Whether you have or plan an EV or heat pump
• Usable capacity, not just the headline capacity
• Maximum charge and discharge power
• Whether backup operation is required

Energy Saving Trust says a typical home system may be around 10 kWh, but there is no universal correct size. A good installer should model your half-hourly usage where available and explain why the proposed capacity is appropriate.

Costs and lifespan

Energy Saving Trust’s July 2026 guidance gives a broad battery cost range of £1,500 to £10,000 and around £4,600 for a 5 kWh system. Typical life is about 10–12 years—shorter than many solar panels—so replacement may be needed during the array’s life.

When a battery is more attractive

• You export a large amount of solar at a low rate and buy it back later at a much higher rate.
• You use substantial electricity in the evening.
• A time-of-use tariff creates a meaningful cheap/peak price gap.
• You value resilience and the chosen system provides genuine backup capability.

Check these details

1. Usable kWh and power output in kW
2. Round-trip efficiency and standby consumption
3. Warranty years, cycles and retained-capacity terms
4. Indoor/outdoor location limits and fire-safety requirements
5. Whether solar operates during a power cut
6. App access, tariff compatibility and ongoing support

Frequently asked questions

Will every battery keep the house running in a power cut?

No. Backup often needs additional equipment and may supply only selected circuits. Get the proposed backup arrangement in writing.

Is a battery essential with solar?

No. Solar works without one. Compare solar-only and solar-plus-battery payback separately.

Independent source

Energy Saving Trust: battery storage