The short answer
Yes. Fox ESS is one of the best-known home battery brands in the UK and a well-proven choice. Its EP12 stores 11.52 kWh in one weatherproof unit with built-in warming, it can be added to existing solar with an AC-coupled inverter, and it usually costs less than premium systems. It doesn’t have EV charging built in, and whole-home backup has a short break of a couple of seconds.
Fox ESS is one of the battery brands people ask us about most. These are the questions that come up, answered plainly by an installer that fits it.
Is Fox ESS any good?
Yes. Fox says industry data puts its share of the UK home solar and storage market at more than 35%, which means mature software, plenty of experienced installers, and a UK service centre in Coventry for support and warranty work. The range is broad: high-voltage EP batteries that pair with Fox hybrid inverters from 3 to 10 kW, three-phase models, and the EVO all-in-one.
Where it is strong:
- Proven. Widely installed, with a UK support base.
- Flexible. Works for new systems and for adding a battery to panels you already have.
- Safety built in. The current EP batteries have built-in fire suppression and battery warming.
- Good value. It usually costs less than Sigenergy or EcoFlow.
Where it is weaker:
- No built-in EV charging. Fox sells separate AC chargers instead.
- Whole-home backup isn’t instant. There’s a short break when the gateway switches over.
- Warranty paperwork. The full term depends on registering the battery and connecting it to FoxCloud.
Where is Fox ESS from?
Fox ESS is a Chinese manufacturer, headquartered in Wuxi in Jiangsu province. In the UK it trades as FoxESS UK Ltd, with its national service centre in Coventry, and describes itself as a Sino-British partnership. Sigenergy, another brand we fit, is also Chinese.
Fox ESS EP11 vs EP12: what’s the difference?
The EP12 is the newer model and the one Fox’s UK range now lists, alongside the smaller EP6. The EP11 (and the EP5) came before. If you’re comparing the two, here’s what changed:
- More storage: 11.52 kWh per EP12 against 10.36 kWh per EP11. Up to four link together: 46 kWh of EP12, against about 41.6 kWh of EP11.
- Built-in warming: the EP12 can warm itself and charge down to minus 25°C with warming on. The EP11 stops charging below 0°C.
- Same family: both are LFP, IP65, wall or floor mounted, and work with Fox’s H1, KH and three-phase inverters.
If you already have an EP11, it’s still a sound battery. For a new install we fit the EP6 or EP12.
Does a Fox ESS battery work in a power cut?
Yes, but how depends on what’s fitted:
- Backed-up circuits. Fox inverters have a backup output (Fox calls it EPS) that keeps chosen circuits, such as the fridge, lights and router, running. It switches over in under 10 milliseconds on the H1-G2 and under 4 on the EVO.
- Whole house. Add Fox’s EPS-BOX-SP gateway and the whole home runs from the battery and panels, within what the system can supply. Fox says there’s a short break, typically 2 to 3 seconds, while it switches.
If neither is wired in, the battery shuts down in a power cut, like most batteries, so tell us at the start if backup matters.
Does Fox ESS work with Octopus?
Yes. Octopus lists FoxESS as “eligible right now” for Charge Pack, its add-on that runs your battery automatically on Intelligent Octopus Go, Octopus Go, Flexible or Fixed import with Outgoing Octopus export. Fox ESS is also on Octopus’s compatible list for Intelligent Octopus Flux, though at the time of writing Octopus says that tariff is only open to customers who bought their solar and battery from Octopus. On other tariffs, you set charge times in FoxCloud. See the best tariffs for solar and batteries.
Can Fox ESS be added to existing solar panels?
Yes, and this is one of Fox’s strengths. The AC1-G2 is an AC-coupled inverter made for retrofits: your panels and their inverter stay as they are, and the Fox battery sits alongside, charging from surplus solar that would otherwise be exported. Fox’s H1-G2 and KH inverters can also run AC-coupled. We check your existing inverter and wiring first. A battery added to existing panels is currently 0% VAT, until 31 March 2027. More in our guide to adding a battery to solar.
What warranty does Fox ESS give?
- EP6 and EP12: 10 years, according to Fox’s UK product page.
- EVO all-in-one: 12 years.
- How it works: Fox’s published UK battery warranty policy gives its EP batteries five years as standard plus a free five-year extension, as long as the battery is registered with Fox and connected to FoxCloud through a Fox datalogger.
- Capacity guarantee: for the EP batteries in that policy, at least 70% of the original capacity at 10 years, or until a set amount of energy has passed through it, whichever comes first.
The practical point: make sure the battery is registered and connected to FoxCloud when it’s installed, because that’s what unlocks the second five years. We confirm the exact terms for your model in your quote.
Can a Fox battery go outside or in a cold garage?
Yes. EP batteries are rated IP65 and the EVO IP66, so both can go outside, in a garage or indoors, on the wall or the floor. For cold garages, the EP12’s built-in warming is the useful bit: with it on, the battery can charge and discharge down to minus 25°C. Fox’s warranty policy does ask for the surrounding temperature to stay between minus 10°C and 50°C, and for 300 mm of clear space around the battery for cooling, so a sheltered spot is best.
How does Fox ESS compare with Sigenergy?
Sigenergy is the more advanced system: DC EV charging in the stack, 0 ms whole-home backup with its gateway, cells rated for 10,000 cycles and room for about 54 kWh. Fox ESS is the proven, lower-cost option, and the easier one to add to solar you already have. We compare them in detail in Sigenergy vs Fox ESS, and our two top picks go head to head in Sigenergy vs EcoFlow.
Our view
Fox ESS is a safe, sensible battery. If you want storage that does the everyday job well, at a fair price, with a big UK support base behind it, it’s hard to argue with. If you have an EV, look at Sigenergy first; if you need backup with no break at all, look at Sigenergy or EcoFlow. Our technical solar designer can design a Fox system for your home on a video call and show you how it compares.
