For the Tesla Powerwall 3 (13.5 kWh) E.ON Next is lowest at £7,795, then EDF at £7,995 and Octopus at £7,999. For a small Sunsynk battery E.ON and EDF both list £3,995 (EDF with an inverter), and Octopus lists a 5 kWh Fox ESS or Enphase battery at £3,947. British Gas sells a battery through Sunsave at £3,629 upfront or £37.50 a month for 120 months (£4,500 in total at 4.5% representative APR), but the page does not say how big the battery is. EDF's prices carry 0% VAT until 31 March 2027. Per usable kWh the large Tesla is the cheapest on every supplier, and a supplier price is a benchmark to check any installer's quote against, not a reason to stop comparing.
The four offers side by side
| Octopus Energy | E.ON Next | EDF | British Gas (with Sunsave) | |
|---|---|---|---|---|
| Entry battery | Fox ESS EVO 5 or Enphase 5P, 5 kWh: £3,947 | Sunsynk Elite, 5.12 kWh (4.6 usable): from £3,995 | Sunsynk with an inverter: from £3,995 (battery alone £2,495) | Battery size not stated: £3,629 upfront |
| Mid size | About 10 kWh (Fox EVO 10 or two Enphase): £5,336 | Two Sunsynk modules | Two Sunsynk sizes (not stated) | Not stated |
| Tesla Powerwall 3 (13.5 kWh) | £7,999 | from £7,795 | from £7,995 | Not stated |
| Warranty | 10 to 15 years by package | 10 years (battery) | 10 years (Sunsynk) | 10 years battery and inverter, plus a 10-year insurance-backed workmanship guarantee |
| Paying | Pay on completion after a £500 deposit; loan option | 0% APR to 3 years, or 7.9% over 5 to 10 | Not stated | £0 deposit, 120 × £37.50 at 4.5% representative APR, or upfront |
| VAT | Not stated | Not stated | 0% until 31 March 2027 | Not stated |
| Read | 6 October | 18 October | 20 October | 20 October |
The pattern is the usual one: the headline prices sit within a few hundred pounds for the same Tesla, and the differences that matter are in the rows below the prices.
Price per usable kWh, where it can be worked out
| Offer | Usable kWh | Price | Per usable kWh |
|---|---|---|---|
| Octopus, 5 kWh Fox EVO or Enphase | 5.0 | £3,947 | about £789 |
| E.ON Next, Sunsynk Elite (with inverter) | 4.6 | £3,995 | about £868 |
| Octopus, about 10 kWh | about 9.7 to 10.0 | £5,336 | about £534 to £550 |
| E.ON Next, Tesla Powerwall 3 | 13.5 | £7,795 | about £577 |
| EDF, Tesla Powerwall 3 | 13.5 | £7,995 | about £592 |
| Octopus, Tesla Powerwall 3 | 13.5 | £7,999 | about £593 |
| British Gas with Sunsave | Not stated | £3,629 | cannot be calculated |
The official DESNZ medians for MCS-certified installs in 2025/26 were £1,300 per kWh for batteries under 6 kWh, £890 for 6 to 11 kWh and £630 for 11 kWh or more, so every supplier price with a stated size is below the median for its band. The British Gas figure is the odd one out: it is the lowest price on the table but it is a price for a battery of unknown size, so it tells you nothing about value until the supplier says how many kWh you get. Ask for the usable capacity in writing.
What each supplier ties you to
- Octopus. Its best battery tariff, Intelligent Octopus Flux, is currently reserved for people who bought both solar panels and a battery from Octopus. Standard Octopus Flux is open to other homes with solar, a compatible battery, a smart meter and an export meter number. It takes a £500 non-refundable deposit when you sign. The Octopus home battery guide has the detail.
- E.ON Next. The battery can be bought separately, but the two discount codes on its page are for existing customers only, and its September £1,000 and £500 promotion ended on 24 September 2026. The E.ON Next battery guide covers the finance maths.
- EDF. Buying a battery with EDF unlocks its Export Exclusive tariff, which the page says pays 18p per kWh exported. The page names the tariff differently in its table and its footnotes, so ask which one applies before you sign. It states the installer as Contact Solar, described as a Which? Trusted Trader.
- British Gas. The offer is sold and installed by Sunsave, which is also the lender; British Gas is the tariff provider and an introducer. The tariff, Store&Save, is fixed for two years and Sunsave’s savings example (a bill falling from £1,279 to £642) does not state its assumptions. Sunsave’s page says the workmanship guarantee is covered by the Renewable Energy Consumer Code (RECC) if Sunsave goes out of business, which is a useful protection to ask any installer about.
Paying: the numbers worth checking
British Gas’s loan is the clearest example of why the total matters. Paying £37.50 a month for 120 months is £4,500 against £3,629 upfront, so the finance costs £871.55 in interest, a 24% premium on the cash price over ten years. That is a fair price for a loan at 4.5% representative APR, but only if you would otherwise pay cash, and only if you keep the battery for the full ten years.
E.ON’s 0% APR over up to three years is the cheapest finance on offer if you can clear the balance in that time. Its longer 7.9% loans cost more: its own example of a £3,995 order with a £998.75 deposit, paid at £35.77 a month for 120 months, comes to £5,291.15, which is £1,296.15 above the price. Octopus offers a fixed-term loan as an alternative to paying on completion. For finance, compare the total payable, not the monthly figure.
What a supplier battery saves
This site’s model, for a London home using 3,000 kWh a year with 4 kWp of solar:
| Battery | Tariff | Modelled saving a year | Simple payback at the supplier price |
|---|---|---|---|
| 5 kWh, Octopus £3,947 | Octopus Flux | £174 | about 23 years |
| 10 kWh, Octopus £5,336 | Octopus Flux | £414 | about 13 years |
| Tesla Powerwall 3, E.ON £7,795 | Octopus Flux | £569 | about 14 years |
| Tesla Powerwall 3, E.ON £7,795 | Flat tariff | £174 | about 45 years |
The saving belongs to the tariff, not the supplier: the same Powerwall saves £569 on a time-of-use tariff and £174 on a flat one. So the useful question to ask any of the four is not what the battery costs but which tariff it is allowed to use and for how long that tariff is guaranteed. The best tariff for a home battery page compares what each pays, and the calculator lets you test your own usage.
Solar and battery packages
If you are buying panels as well, the supplier packages bundle both. Octopus lists a Smart package from £7,915 with four panels and a Fox ESS battery, an Optimised package from £9,187 with four panels and an Enphase battery, a Tesla package from £12,362, and its most popular system, 12 panels with a 10 kWh battery, at £11,115. The other suppliers’ pages in this comparison publish battery and inverter prices without package prices. The solar panels and battery cost guide sets those against independent quotes, and the cost guide shows what each battery size cost across the market in 2025/26.
When an independent quote wins
A supplier is the simplest way to buy and the price is public, which makes it a good benchmark. An independent MCS-certified installer is more likely to win when you want a brand the suppliers do not sell (the suppliers’ range is narrow: Fox, Enphase, Sunsynk and Tesla between them), when you are adding a battery to existing solar with an inverter that must match, when you want a larger system than the supplier offers, or when you need backup that the cheaper packages do not provide. Put the supplier prices above next to at least two written quotes for the same usable capacity, check the VAT line on each, and run the numbers through the quote checklist. The 10kWh battery and 13kWh battery pages compare the sizes across brands, and the Sunsynk and Duracell guides cover two brands the suppliers use or compete with. 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 supplier named here.
Questions people ask
Which energy supplier sells the cheapest home battery?
On published prices, British Gas is lowest at £3,629 upfront through Sunsave, but its page does not state the battery's capacity, so it cannot be compared per kWh. For a stated size, Octopus lists a 5 kWh battery at £3,947 and a 10 kWh at £5,336. For the 13.5 kWh Tesla Powerwall 3, E.ON Next is lowest at £7,795, against EDF at £7,995 and Octopus at £7,999. Compare per usable kWh, not headline price.
Do I need to be a customer to buy a battery from an energy supplier?
Octopus and E.ON Next sell batteries to non-customers on their pages, with discount codes limited to E.ON's existing customers. EDF ties its Export Exclusive tariff to buying a battery with it and does not say on its page whether you must be an EDF electricity customer to buy. British Gas's page does not state a customer requirement either, so ask each supplier before you assume you can or cannot buy.
What is the British Gas home battery offer?
British Gas promotes a battery installed by Sunsave: £0 deposit and 120 monthly payments of £37.50 on a £3,628.45 loan at 4.4% interest (4.5% representative APR, £4,500 in total), or £3,629 upfront. It carries 10-year product warranties on the battery and inverter and a 10-year insurance-backed workmanship guarantee. It is paired with a British Gas tariff that is fixed for two years. Sunsave is the installer and lender; British Gas acts as an introducer for a fixed referral fee.
Are supplier batteries cheaper than an independent installer?
Sometimes, for a standard job. Supplier prices are published 'from' prices and a survey can move them, but they are all below the official median per kWh for their size. An independent MCS-certified installer prices the specific home and can quote any brand or size. Get at least three written quotes for the same usable capacity and divide each by usable kWh.
Is 0% VAT included in supplier battery prices?
EDF says its prices are available with 0% VAT until 31 March 2027. Octopus and E.ON Next do not say whether their listed prices include VAT, so ask for the quote to show no VAT on an installed battery. Zero-rating for installed batteries is temporary and ends on 31 March 2027.
Which supplier battery has the longest warranty?
On their pages, Octopus lists up to 15 years on its Enphase battery packages, 12 years on Fox ESS packages and 10 years on the Tesla. E.ON Next and EDF list 10 years on the Sunsynk, and British Gas's Sunsave offer lists 10 years on the battery and inverter plus a 10-year insurance-backed workmanship guarantee. A longer warranty is only as good as the company behind it.