A battery stores the sun you make at midday, so you can use it at night. Whether that's worth a few thousand pounds depends on two things most adverts skip: your tariff, and what you're paid for the power you export.
How much does a solar battery cost in the UK?
Adding a home battery to a solar system usually costs about £2,000 to £5,000, depending on its size. Our savings calculator uses £3,500 as a middle figure. If an installer fits it, you pay 0% VAT until 31 March 2027. After that the rate goes to 5%.
What does a battery actually do for your bill?
It lets you use more of your own power. Without a battery, a typical home uses about 40% of the solar it makes. The rest goes to the grid. With a battery, that share rises to about 70%. Each kWh you use yourself saves you the full price of buying one, which is 26.32p under the Ofgem cap for October to December 2026.
What do the sums look like?
Take a 4 kWp system that makes about 3,600 kWh a year. A battery moves about 1,080 kWh a year from exported to used. If you'd have been paid 12p to export it, each kWh is worth 14p more used at home. That's about £155 a year. If your export rate is only 4p, the gain is about £240 a year. On a £3,500 battery, that's roughly 15 to 23 years from solar alone.
So why do people say batteries pay back faster?
Because of tariffs. A time-of-use tariff sells power cheaply at night and dearly in the evening. A battery can fill up on the cheap rate, as well as on solar, and cover the dear hours. That second job can save more than the first, mostly in winter when the panels are quiet. Ask your installer to show both savings on separate lines of the quote.
What's the peace-of-mind case?
If power cuts are common where you live, a backup-ready battery recharges itself every morning. That's worth something even when the sums are so-so. Not every battery can do this, though. Backup needs extra kit, so ask for it by name if you want it.
Should you get the battery now or later?
You can add one later. Most systems can take a battery after the panels go in. If you're unsure, fit the panels, watch a year of real numbers, then decide. The one reason to hurry is the 0% VAT, which ends on 31 March 2027.
The quick version
- A battery costs about £2,000 to £5,000 on top of the panels.
- It lifts your own solar use from about 40% to about 70%.
- It pays best on a time-of-use tariff or a low export rate.