Five UK retailers listed the Fox ESS EVO 10 with a 5 kW inverter and 10.24 kWh of battery at £2,880 to £3,356 before VAT on 7 October 2026, with a median of £3,158, which is £3,456 to £4,027 with 20% VAT. Octopus's installed price for about 10 kWh is £5,336, with no VAT because installed home batteries are zero-rated until 31 March 2027. On that comparison the hardware is about 54% to 63% of the installed price, and the other 37% to 46%, roughly £1,980 to £2,460, pays for installation, commissioning, paperwork and the supplier's margin.
Analysis · Published by SEO Dons Ltd · Updated 7 October 2026
The box: five retail listings
The Fox ESS EVO is sold to installers through UK distributors and trade shops, and several publish a price. We read every retailer’s page for the same product, the EVO 10 with a 5 kW inverter and 10.24 kWh of battery (Fox’s code EVO10-5-H), on 7 October 2026. Prices before VAT are the fair basis, because a trade buyer reclaims it:
| Retailer | Price before VAT | With 20% VAT |
|---|---|---|
| The Eco Supermarket | £2,880.00 | £3,456.00 |
| Solareon | £3,098.60 | £3,718.32 |
| AIZO Quality Heating | £3,158.33 | £3,790.00 |
| ITS Technologies | £3,192.00 | £3,830.40 |
| Solar Trading UK | £3,355.80 | £4,026.96 |
The median is £3,158 before VAT and the range £476. Two retailers, AIZO Quality Heating and The Eco Supermarket, show both prices on the page; the other three list a price before VAT, and we added 20% to get the right-hand column. Some listings were on sale, so these are the prices on the day, not a standing price.
The installation: Octopus’s price for the same size
Octopus publishes a battery-only installed price of £5,336 for about 10 kWh, which it fits with either a Fox EVO 10 or two Enphase IQ Battery 5P units (April 2026 prices). It is an installed price with no VAT, because installed home batteries are zero-rated until 31 March 2027. Putting the two side by side:
| Amount | Share of £5,336 | |
|---|---|---|
| Retail hardware, before VAT, lowest to highest | £2,880 to £3,356 | 54% to 63% |
| Left for installation, paperwork, warranty cover and margin | £1,980 to £2,456 | 37% to 46% |
This is a comparison, not Octopus’s cost sheet. A supplier that buys in volume pays less than a retail listing, so the hardware share of its price is probably lower than this and the rest correspondingly higher, and the Fox EVO is not the only option at that price, since two Enphase units are the alternative.
Why VAT changes the comparison
For a trade buyer the VAT on hardware is a wash. For a homeowner it is not. A battery supplied and fitted in a home by a VAT-registered installer is zero-rated until 31 March 2027 and then charged at 5%, according to HMRC’s VAT Notice 708/6. A battery bought on its own is charged at the standard 20%. That is why the same box shows two prices on the retailers’ pages, and why buying hardware yourself and finding an electrician is not a saving of the whole difference: you add £576 to £671 of VAT to the box, and the labour is a separate bill.
What the rest of the price has to cover
Every item below is something a competent installer does for a Fox EVO, and each is a line to ask about:
- A survey and a location that meets PAS 63100. The fire-safety specification for batteries in homes rules out bedrooms, escape routes and lofts, which can change the cable route and the cost.
- Fitting and wiring to the consumer unit, with a lockable isolator, and any consumer unit work.
- Commissioning and set-up of the app and the tariff.
- The network notification. A system within 16 A per phase, about 3.68 kW counting every inverter, is notified within 28 days of commissioning. The EVO 10’s 5 kW inverter is above that, so expect a G99 application before installation, which takes time and may bring an export limit.
- Certification. An MCS certificate under MIS 3012 and an electrical certificate with a PAS 63100 statement.
- The warranty route. Fox’s policy says only the installer and Fox ESS authorised staff can claim, and excludes installation by a non-accredited installer, so the installer’s own financial health and guarantee are part of what you are buying.
Where the unit can go decides how much of this applies. The room-by-room siting table shows which spaces the fire-safety specification allows, and which need fire separation or an outdoor mounting.
How to use this
When a quote lands, split it. Ask for the model and inverter rating, the hardware price, the installation price and the VAT treatment on separate lines. As a rough benchmark, Octopus’s £5,336 puts the part of an installed EVO 10 that is not hardware at about £2,000 to £2,500. A quote far above that deserves a line-by-line explanation, and one far below it is worth checking for what is missing, such as the network application or the certificate. Then check the whole price against the official median of £890 per kWh for a 6 to 11 kWh battery, which our page on 10kWh batteries does for five products, and compare it with the supplier prices in our guide to Octopus’s home batteries. Our page on the Fox ESS battery covers the EVO and EP ranges, the warranty and what a claim involves, and you can ask for battery storage quotes (we reply by email) to compare.
The solar battery cost guide puts the same split next to the official medians and the average installation in each size band.
Questions people ask
How much does a Fox ESS EVO 10 cost to buy without installation?
Between £2,880 and £3,356 before VAT at five UK retailers on 7 October 2026, for the version with a 5 kW inverter and 10.24 kWh of battery. With 20% VAT that is £3,456 to £4,027. The median of the five was £3,158 before VAT.
Why is an installed Fox EVO more expensive than the retail hardware price?
The installed price also pays for a survey, the fitting and wiring, commissioning, the notification to the network operator, the certification paperwork, the installer's insurance-backed guarantee and the supplier's margin. On Octopus's £5,336 for about 10 kWh, those come to roughly £1,980 to £2,460 once retail hardware prices are taken off, although a large installer pays less than a retail listing.
Do I pay VAT on a Fox ESS battery?
It depends how you buy it. A battery supplied and installed in a home by a VAT-registered installer carries 0% VAT until 31 March 2027, then 5%. A battery bought without installation carries the standard 20%, which is why the retail listings show a price before VAT and a price including it.
Is it cheaper to buy a Fox EVO and have an electrician fit it?
Not necessarily. You would pay 20% VAT on the hardware, lose the 0% rate on the installed supply, and take on checking MCS certification, the network notification and the warranty route: Fox's policy says only the installer and Fox ESS staff can make a claim, and excludes installation by a non-accredited installer.