For most homes with new or existing solar and a time-of-use tariff, the Tesla Powerwall 3 is the best value large battery: 13.5 kWh at £7,795 to £7,999 installed (about £577 to £593 per usable kWh) with a 10-year, 80% warranty. For adding a small, simple battery to existing panels, the Enphase IQ Battery 5P has the longest warranty (15 years). For a 10 kWh battery at the lowest price, Octopus's Fox ESS EVO 10 is £5,336 (about £550 per usable kWh). The battery to avoid buying new is anything whose maker has failed: GivEnergy's 12-year warranty is not being honoured since the April 2026 administration.
The picks at a glance
| Situation | Best pick | Installed price | Per usable kWh | Warranty |
|---|---|---|---|---|
| Large battery, new or existing solar, time-of-use tariff | Tesla Powerwall 3, 13.5 kWh | £7,795 (E.ON) to £7,999 (Octopus) | about £577 to £593 | 10 years, 80% retained |
| 10 kWh at the lowest published price | Fox ESS EVO 10 (Octopus), about 9.7 kWh usable | £5,336 | about £550 | 12 years |
| Small add-on to existing panels, longest warranty | Enphase IQ Battery 5P, 5 kWh | £3,947 (Octopus) | about £789 | 15 years or 6,000 cycles, 60% retained |
| Lowest-cost entry battery | Sunsynk Elite, 4.6 kWh usable | from £3,995 (E.ON, EDF) | about £868 | 10 years |
| No solar panels, tariff-led | 10 kWh (Fox EVO 10 or two Enphase) on Agile Octopus | £5,336 | about £534 to £550 | 12 or 15 years |
Prices are the suppliers’ published “from” prices, which a survey can move. The official DESNZ medians for MCS-certified installs in 2025/26 were £1,300 per kWh under 6 kWh, £890 for 6 to 11 kWh and £630 for 11 kWh or more, so each pick above is below the median for its size. The supplier comparison lists every supplier’s price side by side.
If you have new solar or want one big battery: Tesla Powerwall 3
The Powerwall 3 is 13.5 kWh with a built-in solar inverter, so it can take the panels directly and run the house in a power cut when it is fitted with Tesla’s backup gateway. Its warranty is 10 years with 80% of capacity retained, with unlimited cycles for solar self-consumption, time-of-use shifting and backup, though Tesla’s full term depends on the battery staying connected to the internet. On price, E.ON Next’s £7,795 is the lowest published installed figure, with EDF at £7,995 and Octopus at £7,999. In this site’s model it saves about £569 a year on Octopus Flux for a home using 3,000 kWh with 4 kWp of solar (payback about 14 years) and only £174 on a flat tariff, so it is the pick only if you can use a time-of-use tariff. The Powerwall 3 guide has the specs, the gateway and the warranty conditions.
If you want 10 kWh for the least money: Fox ESS EVO 10
Octopus installs a Fox ESS EVO 10 (10.24 kWh, about 9.7 kWh usable) for £5,336 at April 2026 prices, about £550 per usable kWh, and Fox’s own UK policy gives EVO batteries 12 years. It saves about £414 a year in the model with 4 kWp of solar on Flux, a payback of about 13 years, the shortest in this guide. Two cautions: Fox sells the EP series with a 10-year warranty as well, so confirm which you are being quoted, and Octopus’s best battery tariff is reserved for its own customers. The Fox ESS guide covers the EP and EVO differences, and the 10kWh battery page compares every brand at that size.
If you are adding to existing panels: Enphase IQ Battery 5P
The 5P is AC-coupled, so it connects to the home’s wiring like an appliance and leaves the solar inverter untouched, which is why it suits a retrofit. Its UK warranty runs 15 years or 6,000 discharged cycles, whichever comes first, with at least 60% of nameplate capacity guaranteed, the longest of any battery sold by the big suppliers. At £3,947 for 5 kWh it costs about £789 per usable kWh, so buy two for 10 kWh at £5,336 (about £534). If your existing panels are on a different inverter, an AC-coupled battery is usually the simpler route; the AC against DC guide explains when it is not.
If you only have a small budget: the cheapest is not the best value
The Sunsynk Elite at £3,995 (4.6 kWh usable) and Octopus’s 5 kWh at £3,947 are the lowest prices, but a 5 kWh battery costs the most per kWh and saves the least, £162 to £174 a year in the model, a payback of about 23 to 25 years. If the budget is below about £5,000 and you have solar, a single module is a way to start, not a way to repay itself. Buy it only if the system can be extended later: the Sunsynk Elite stacks to six modules, and the Sunsynk guide explains the warranty differences between its product lines.
If you have no solar: pick the tariff first
Without panels, a battery earns by charging at cheap rates and discharging at dear ones. A 10 kWh battery on Agile Octopus saves about £335 a year in the model, a payback of about 16 years, and on Octopus Go with an electric car about £503 for the larger sizes. Choose the tariff, then the battery that supports it; the battery without solar guide tests Agile on 12 months of real prices.
The batteries to approach with caution
- GivEnergy. The 12-year warranty on its batteries was given by GivEnergy Ltd, which entered administration on 9 April 2026; the administrator says no further hardware warranties will be honoured. A GivEnergy battery already on a wall keeps working, but buying one now means no manufacturer behind it. See what happened to GivEnergy.
- Licensed and distributed brands. The Duracell home battery is made and warranted by Puredrive Energy under licence, and Sunsynk is sold in the UK through Sunsynk UK Ltd. Both are active companies with filings, and both are conventional lithium iron phosphate products, but their 10-year warranties rest on a single company, so ask who pays a claim.
- A battery that your tariff will not accept. Octopus Flux asks for a compatible battery and an MCS certificate. Ask your supplier in writing before you buy.
How to choose between them
- Decide the tariff you can use. On a flat tariff no battery repays within its warranty, and on Octopus Flux or Agile the better ones repay in 13 to 16 years.
- Decide the size. Work out what you use after dark; the what size guide shows where extra capacity stops paying.
- Compare per usable kWh and check the VAT. Installed batteries carry 0% VAT until 31 March 2027, and the cost guide shows what each size cost across the market in 2025/26.
- Check the company behind the warranty, not just the years.
Three written quotes for the same usable capacity is the simplest protection; the quote checklist shows what to put side by side. If you would like a reply by email, send a battery storage quotes request. This site does not install batteries and is not affiliated with any maker or supplier named here.
Questions people ask
What is the best solar battery in the UK?
For a large battery on a time-of-use tariff, the Tesla Powerwall 3 at £7,795 to £7,999 installed is the best value, at about £577 to £593 per usable kWh against an official median of £630 for batteries of 11 kWh or more. For a 10 kWh battery, a Fox ESS EVO 10 at Octopus's £5,336 is about £550 per usable kWh. For a small add-on to existing panels, the Enphase IQ Battery 5P has a 15-year warranty. The right choice depends on your panels and tariff.
Which solar battery has the longest warranty?
Of the batteries suppliers sell in the UK, the Enphase IQ Battery 5P: 15 years or 6,000 discharged cycles, whichever comes first, guaranteeing at least 60% of nameplate capacity. Fox ESS gives 12 years on the EVO and 10 on the EP, Tesla 10 years with 80% retained, and Sunsynk and Duracell 10 years. A warranty is only as good as the company behind it: GivEnergy's 12 years is not being honoured after its administration.
How big a solar battery do I need?
Most homes using about 3,000 kWh a year are well served by 5 to 10 kWh. In this site's model a 10 kWh battery saves about £414 a year on Octopus Flux with 4 kWp of solar, against £174 for a 5 kWh battery, and a 13.5 kWh Powerwall 3 saves about £569. Beyond the amount you use after dark, extra capacity adds little. The what-size guide shows where the saving levels off.
Is a solar battery worth buying?
On a flat tariff, no: a battery only stores spare solar and pays back in 25 years or more. On a time-of-use tariff such as Octopus Flux, a 10 kWh battery in this site's model repays in about 13 years and a Powerwall 3 in about 14. Without solar, a 10 kWh battery on Agile Octopus saves about £335 a year, a payback of about 16 years. The tariff decides it more than the brand.
Should I buy the cheapest solar battery?
Not on headline price. A 5 kWh battery costs about £790 to £870 per usable kWh and saves only £162 to £174 a year in this site's model, so it repays slowly even though it is the cheapest to buy. Compare per usable kWh, check what the warranty guarantees, and check who stands behind it.
Which batteries should I avoid?
Any battery whose maker or warranty provider cannot honour the warranty. GivEnergy Ltd entered administration on 9 April 2026 and its administrator says no further hardware warranties will be honoured. For licensed or distributed brands such as Duracell (made and warranted by Puredrive Energy) and Sunsynk (through Sunsynk UK Ltd), the batteries are conventional but you should ask who pays a claim in year eight.