Guide · Batteries
Fox ESS EP6 vs EP12: which one do you actually need?
Last updated: 5 October 2026 · Written by the ECONEXIS team, MCS-accredited installers.
For most three-bed homes with solar, the EP12. The EP6 only wins if your evening use is genuinely small, or the budget is fixed and a battery at all beats no battery.
- EP6 — 5.76 kWh · from £6,890 installed with 10 panels
- EP12 — 11.52 kWh · from £7,990 installed with 10 panels
- The difference is £1,100 for double the storage
- Already have a hybrid inverter? One battery fitted: EP6 from £1,990 · EP12 from £2,790
How our prices work: package prices are for panels on one roof face with a single scaffold lift. Your fixed price comes with your free roof design, based on your roof type, how many roof faces the panels sit across, the scaffolding needed and where the battery goes. No guessing, no surprises on the day.
Which is you? Pick the closest.
Small home, out all day
Flat or two-bed, gas heating, evenings are lights, TV and cooking.
→ EP6. Enough to carry a light evening; a bigger battery would sit half-full.
Three-bed, someone home in the evening
Dishwasher, washing machine, an electric oven, screens, a busy 5–10 pm.
→ EP12. This is the typical family evening, and the EP6 runs out before bedtime.
EV, heat pump, or planning one
Anything that charges or heats overnight on a cheap tariff.
→ EP12, and plan for a second. This is what stacking is for.
Side by side
| Fox ESS EP6 | Fox ESS EP12 | |
|---|---|---|
| Capacity | 5.76 kWh | 11.52 kWh |
| Chemistry | LFP (lithium iron phosphate) — the stable, long-life chemistry home storage has standardised on | |
| Grows by adding | another EP6 (11.52 kWh, then 17.28) | another EP12 (23 kWh, then 34.5) |
| Can the two be mixed? | No. Different size classes; a stack is all EP6 or all EP12 | |
| Placement | Floor-standing, rated for outdoor installation — garage, side wall or utility | |
| Warranty | 10 years (Fox ESS), plus our IWA insurance-backed workmanship guarantee | |
| One battery, fitted to your existing hybrid inverter | £1,990–£2,390 | £2,790–£3,390 |
| One battery with a new hybrid inverter, fitted | £3,290–£3,890 | £4,290–£4,890 |
| In our packages | Smart — from £6,890 | Plus — from £7,990 |
Package prices: 10 × 470 W all-black panels, 0% VAT, based on one roof elevation with a single scaffold lift. Extra roof faces or scaffolding are quoted at survey. Capacity figures are the manufacturer's.
What we see on installs
The photo below is a Romford job: a Fox ESS battery bank and hybrid inverter on a garage wall, cabled and labelled. Two things customers notice in the first month that no spec sheet tells you.
- The EP12 is the one people stop thinking about. With ~11.5 kWh the evening is simply covered; nobody is watching the app to see if it will last until bed. EP6 owners in a busy house do watch it.
- Wall space is real. An EP12 is one tall unit. Two EP6s to reach the same capacity are two units, two brackets and more wall — which is why "two small ones" is rarely the right answer.
The mistake to avoid
EP6 and EP12 cannot be combined later. If you start with an EP6 hoping to "add an EP12 when there's money", you cannot — you would be adding another EP6 or replacing the lot. Choose the family once. If there is any chance your electricity use grows (a car, a heat pump, a bigger family), that decides it: EP12.
Who each one is for, plainly
EP6: a smaller household with a light evening load, or a fixed budget where a battery at all is the win. It is a good battery; it is just a small one.
EP12: the typical family home, anyone with or planning an EV or heat pump, and anyone who would rather not think about it. It is the battery we install more than any other, for that reason.
Still not sure? We size it in your free roof design from your actual electricity use — the answer is in your bill, not in a guess. No pressure, no obligation.
EP6 vs EP12 — common questions
Can I start with an EP6 and add an EP12 later?
No. The EP6 and EP12 are different size classes and cannot share a stack. You can add another EP6 to an EP6, or another EP12 to an EP12 — but you choose the family once, at the start.
Is two EP6s the same as one EP12?
Exactly the same capacity (11.52 kWh either way) but not the same job: two units, two brackets, more wall space, and usually more money than one EP12. If you want EP12 capacity, buy an EP12.
Which one is in your packages?
Both. The Smart package carries an EP6 (from £6,890 installed); the Plus package carries an EP12 (from £7,990 installed). Both are 10 panels at 0% VAT, based on one roof elevation with a single scaffold lift.
Do both work without solar panels?
Yes. Either can charge on a cheap overnight tariff and run the house through the expensive hours. The choice between them is the same question: how much of your evening do you want covered.
What is the warranty on each?
Ten years on both, from Fox ESS, plus our insurance-backed workmanship guarantee through IWA.
Get started
Not sure which? We size it in your free roof design and fixed price.
Tell us about your home and we'll come back with the right battery for how you actually use electricity.
0% VAT on solar & battery until March 2027