Home batteries: what they save
Figures updated 15 November 2026
A 13.5 kWh battery costs about £8,505 installed. In none of the cases below does it pay for itself over 20 years once you count a replacement after 10 years. It comes closest with an electric car, whose cheap overnight tariff (Octopus Go here) the battery can also use.
| Home | Battery adds a year | Over 20 years |
|---|---|---|
| No solar, no electric car | £0 | −£17,010 |
| Added to solar panels | £156 | −£13,885 |
| No solar, with an electric car | £534 | −£6,334 |
A gas-heated semi in Birmingham, compared with the best option without a battery (same solar, same car, best tariff). The 20-year figure includes a replacement battery after 10 years at today's price. Electricity prices from April 2027, when VAT is due to return.
Why the tariff matters
A battery saves money by moving electricity from when it's cheap to when it's dear. With solar panels it stores what you'd otherwise export (£156 a year in the example, on Octopus Flux Import). On an overnight tariff it fills up at the cheap rate and runs the house through the day (£534 a year on Octopus Go). Without either, there is nothing for it to move.
How long batteries last
Tesla's Powerwall warranty in the UK runs for 10 years and promises 80% of the original capacity at the end. Warranty.
What it costs
The median installed price for home batteries of 11 to 30 kWh was £630 per kWh in 2025/26 (Apr 2025 to Mar 2026), from MCS records published by DESNZ. Source.