A battery does not generate electricity. It moves it in time. Understanding that one point tells you almost everything about whether one is worth having.
92% of UK battery installations in 2026 went onto properties with solar, and around 36000 batteries were certified in the first half of the year. A battery is no longer an unusual extra. For most people getting solar quotes it is part of the same decision.
Figures from the Microgeneration Certification Scheme (MCS). Last reviewed 6 Nov 2026.
What a battery actually does for you
Two things, and the second is now often worth more than the first.
It stops you exporting cheaply Without a battery, solar you are not using goes to the grid and earns you an export rate, which is roughly half what you pay to buy electricity. A battery stores it so you use it yourself in the evening at the full value.
It lets you buy electricity when it is cheap On a time-of-use tariff you can charge the battery overnight at a low rate and run the house off it during the expensive part of the day. This works even in winter when the panels are producing very little, and it works even if you have no panels at all.
The second of these is why batteries have grown so quickly, and it is the part most older solar content misses entirely. It is covered on smart tariffs.
What they cost
A battery of £3,500 to £5,500 buys you roughly 4 to 5kWh of storage. Solar and battery together for a typical house runs £10,100 to £13,900.
VAT on an installed battery is currently 0% until 31 Mar 2027, and a battery qualifies on its own. You do not need to install solar at the same time.
Prices are indicative ranges, last reviewed 6 Nov 2026. Only a quote is a price.
Sizing one
The common mistake is sizing the battery to the solar system. Size it to your evening and overnight electricity use, because that is what it is covering.
Rough approach:
- Look at your annual consumption in kWh, on your bill. Divide by 365 for a daily average.
- Estimate the share you use outside daylight hours. For most households it is more than half.
- That is the ballpark of useful storage. A typical UK home lands somewhere between 5kWh and 10kWh.
Two things to check in a quote:
- Usable capacity, not headline capacity. A battery is not run from completely full to completely empty. The usable figure is lower and it is the one that matters.
- Power output in kW, as well as capacity in kWh. Capacity is how much it holds. Power is how fast it can deliver. A battery with plenty of capacity but low output cannot run an oven and a kettle at once.
Bigger is not automatically better A battery that never fully cycles is capital sitting idle. If you are on a time-of-use tariff and charging overnight, a larger battery does more work than it would on solar alone, because it gets filled every night regardless of the weather.
The installation rules changed, and they matter
BS 7671:2018+A4:2026, published on 15 Apr 2026, introduced Chapter 57, the first dedicated rules the UK wiring standard has had for battery installations. It draws on PAS 63100:2024. Since 15 Oct 2026, when the previous edition was withdrawn, new installations have had to comply.
A loft is not a compliant location Lofts get very hot in summer, are poorly ventilated, sit close to combustible material and are difficult to reach in an emergency.
Where a battery can go:
- Outdoors where practical, on an external wall or in a ground-mounted enclosure, at least 1 metre from doors, windows, vents and escape routes
- A detached garage or outbuilding
- An attached garage with fire-resisting separation from the house
- Indoors only in a room that is not a bedroom, escape route or loft, with 30-minute fire separation and ventilation to outside
The new rules cover new installations If your battery went in before them, it was installed to the standard in force at the time. If it is in a loft and you are uneasy, an electrician can assess it.
If an installer proposes putting a battery in your loft, ask them directly how the installation complies with BS 7671 Amendment 4. Full detail on battery safety and siting.
Source: BS 7671:2018+A4:2026 and PAS 63100:2024. Checked 6 Nov 2026. Confirm current requirements with your installer.
Will it keep the lights on in a power cut?
Usually not, unless it was specified to.
A standard battery and inverter shut down in a power cut, for the safety of people working on the network. Backup requires additional equipment and a separate circuit, and it costs more. If that matters to you, say so before you get quotes rather than after. See solar panels in a blackout.
Do you need solar to have a battery?
No. A battery on its own, charged on a cheap overnight rate, can be worth having. It is a different proposition with different arithmetic, covered on batteries without solar.
What to ask
- Usable capacity in kWh, and power output in kW
- Where exactly it will be sited, and how that complies with BS 7671 Amendment 4
- Warranty length, and whether it is stated in years, cycles or throughput
- What happens to the warranty if the manufacturer leaves the UK market
- Whether it supports time-of-use charging, and whether it does so automatically
- Whether backup in a power cut is included, and what it would cost
- Whether the inverter is separate or built in, and what replacing it involves