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Is a home battery worth it?
Check it with your numbers.
Calm, checkable sums for homeowners in England and Wales. Put in your own quote and tariff. See the answer, and the maths behind it. Nothing you type leaves this page.
Calculator
Home battery calculator
Start simple. Open Advanced when you want every number.
On these numbers
On these numbers this quote takes about 26.7 years to pay back. That is longer than the 10 years you chose for the battery's life. For a 10-year payback, the price you pay would need to be about £2,550.
A straight line: each year counts as the average year, with wear averaged over the battery's life. The band is a scenario, not a forecast. Before interest and replacing parts.
Show the maths
These steps use the numbers set on the left and change as you change them. They are shown so you can check the maths.
VAT and tariff checks
What this leaves out
Interest if you pay monthly and replacing parts would both lower the result. Standby power would lower it too: set it in Advanced. A fixed daily charge is the same with or without a battery, so it does not change the saving. Tariff changes could move the result either way. Example maths. Not financial advice.
Labels: ✓ Documented source and date shown · ◆ Chosen an example value · ? Unknown check the data sheet or the source. How to read them
Sources
What is fact, what is chosen, what is unknown
✓ Documented
- 0% VAT on supply and installation of a battery without solar until 31 March 2027, then 5%: HMRC VAT Notice 708/6, as of 2 November 2026.
◆ Chosen
- 4,200 kWh a year, model household. £6,800 example quote. 10 kWh battery.
- 1 kWh of other use in the cheap night hours. 7 hours of cheap power a day.
- 10 years of life and 70% capacity left at the end, which averages 85% over the life.
- Rounding the first year to the nearest £10, as in video 3 (a switch).
? Unknown
- 26.32p single rate: Ofgem price cap, 1 October to 31 December 2026. Not yet re-checked against Ofgem's page.
- 14.19p night and 32.65p day: Octopus Flexible Economy 7 from 1 October 2026, GB average. One supplier's rate, not every Economy 7 tariff. Not yet re-checked.
- Usable share, round-trip efficiency and standby power of your battery: see its data sheet.
- Rates for cheap-night tariffs: none are included. Type your own.
Data as of 11 November 2026. Prices and tariffs change, so check your own. The next Ofgem price cap is expected around 25 November 2026 (to be confirmed); the example prices will then be updated. Found a mistake? See Corrections.
The sums are the same ones used in videos 1 and 3. The code, text and images on this site may not be reused without permission. How we work out the numbers.