Fox ESS EP6 (AC-coupled, wall/floor-mounted):
- 6.14 kWh per unit
- AC-coupled (works alongside any existing solar inverter)
- Continuous power: 3.6 kW
- Stackable: up to 4 in parallel (24 kWh total)
Fox ESS EP6, EP12 and EVO10 Battery Storage
Fox ESS is the mid-market sweet spot. Strong specs, fair pricing, easy retrofit, broad inverter compatibility. We install a lot of Fox - it works and the maths work.
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Google Rating: 4.5
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Fox ESS EP12 (AC-coupled, wall/floor-mounted):
- 12.28 kWh per unit
- AC-coupled (works alongside any existing solar inverter)
- Continuous power: 5.0 kW
- Stackable: up to 4 in parallel (49 kWh total)
Fox ESS EVO10 (hybrid inverter + battery, all-in-one):
- 10.36 kWh battery + 10 kW hybrid inverter built in
- DC-coupled solar (up to 15 kW PV input)
- Continuous power: 10 kW
- Peak power: 13 kW
- Whole-home backup with EPS box
Headline specs
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Fox ESS EP6 / EP12:
- Chemistry: LFP (lithium-iron-phosphate)
- Round-trip efficiency: 95%
- Cycle life: 6,000+ cycles to 80% State of Health
- IP rating: IP65 (outdoor rated)
- Operating temp: -10C to +55C
- Dimensions (EP6): 580 x 350 x 290 mm
- Dimensions (EP12): 580 x 600 x 290 mm
- Weight (EP6): 67 kg
- Weight (EP12): 130 kg
- Warranty: 10 years to 80% capacity retained
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Fox ESS EVO10:
- Battery: 10.36 kWh LFP
- Solar input: up to 15 kW (2 MPPTs)
- Continuous AC: 10 kW
- Peak AC: 13 kW
- Backup: whole-home with EPS box (continuous 10 kW, peak 13 kW)
- IP rating: IP65
- Dimensions: 750 x 850 x 260 mm
- Weight: 165 kg
- Warranty: 10 years on inverter, 10 years to 80% on battery
Why we install a lot of Fox
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Easy AC-coupled retrofit
EP6 and EP12 are designed for retrofit. They sit alongside your existing solar inverter (any brand), draw power off the AC side, store it, and discharge it back when needed. No solar inverter changeover. No FIT registration risk. Quickest install.
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Pricing
Fox is competitive on £-per-kWh. EP6 from around £4,800 and EP12 from around £7,200 - sometimes the best value option for retrofit.
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Strong app
The Fox app is genuinely good - clear daily energy flow, configurable schedules, smart tariff support, peak shaving controls.
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Stackable
Up to 4 EP6 or EP12 units in parallel. Start with one, add later. Useful for households planning to grow.
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EVO10 is a serious all-in-one option
10kW inverter, 10kWh battery, whole-home backup, all in one box, at a price below Powerwall 3 and Sigenergy. Strong choice for new-install homes.
Where Fox makes sense
Best for:
Retrofit installs (EP6 and EP12 are designed for this), customers who want a quality battery at a sensible price point, mid-size households (3-4 bed), and people who want stackable expansion without paying the Sigenergy premium.
Less ideal for:
Customers who want full 25-year future-proofing (Fox's 10-year-to-80% warranty is good but Sigenergy's 15-year is longer), or installs where the absolute best whole-home backup capability is needed (Tesla and Sigenergy edge it on continuous power).
EP6 vs EP12 vs EVO10 - which one?
| Scenario | Recommended |
|---|---|
| You already have solar, want a 5-7kWh retrofit, small house | EP6 |
| You already have solar, want 10-12kWh retrofit, family home | EP12 |
| You want bigger (>12kWh) for heat pump or EV | 2x EP12 in parallel (24.5kWh) |
| New install, no existing solar | EVO10 (gets you inverter, battery and backup in one box) |
| New install, large solar (8kW+) | EVO10 or two units in parallel |
| You want full whole-home backup | EVO10 with EPS box, or 2x EP12 |
Compatibility
EP6 and EP12 are AC-coupled, meaning they work with any existing solar inverter (Solis, Fronius, SolarEdge, SMA, Tigo, Enphase, Sungrow, Huawei, GoodWe, etc). They have their own battery management and inverter built in. Plug them into the AC side of your home and they work.
EVO10 is a hybrid inverter, so it would replace your existing solar inverter. Best as a new install or as part of an inverter upgrade.
Smart tariffs: all Fox batteries support Octopus Flux, Cosy, Go and equivalent two-rate or three-rate tariffs. EVO10 also supports Octopus Agile via Foxxy and OctoPlus integrations.
Where it lives
IP65 rated. We install Fox batteries in garages, utility rooms, internal cupboards, side walls and outbuildings. EVO10 is the largest unit (165 kg) and usually wants a solid wall or floor pad.
Indicative pricing
| System | Indicative supply + install | Notes |
|---|---|---|
| Fox EP6 retrofit (6kWh, AC-coupled) | from £4,800 | Smallest, cheapest retrofit |
| Fox EP12 retrofit (12kWh, AC-coupled) | from £7,200 | Most popular Fox config |
| Fox 2x EP12 retrofit (24kWh) | from £12,500 | Heat pump or large family home |
| Fox EVO10 new install (10kW inverter + 10kWh battery) | from £9,800 | New solar + battery combo |
| Fox EVO10 + 5-6kW solar combined system | from £14,500 | Full new install package |
Prices vary with site complexity. Your survey gives you the actual number.
Warranty in plain English
Fox warrants the battery to retain 80% of capacity for 10 years (a tougher commitment than the more common 70% threshold). Inverter warranty is 10 years. Greenscape Energy's workmanship warranty is 10 years. The Fox UK team is responsive and we have a direct line to their technical support for warranty claims.
What we have learned from installing them
Fox has been on our line-up since 2021. Observations:
- EP6 and EP12 are particularly clean retrofit batteries. The customer keeps their existing solar inverter and adds Fox alongside. Install is usually 4-6 hours.
- EVO10 is competitive on price against Tesla Powerwall 3 (around £8,900 for Powerwall, around £9,800 for EVO10 with EPS) but the continuous power, app and brand profile of Tesla are stronger for premium customers. EVO10 wins on £-per-kWh and is the right choice when value is the priority.
- We have had a small number of EVO10 firmware glitches over the years - resolved by remote updates. Hardware has been very reliable.
- Fox UK warranty handling is good. We have had three cell-pack replacements in 4 years; all were resolved within 2-3 weeks.
Ready to talk?
Book a Fox ESS survey or call 01473 727 727.
Showroom:
The Energy Shop, 544–550 Woodbridge Road, Ipswich, IP4 4PN.
Open 8am to 5:30pm Monday to Thursday, 8am to 4:30pm Friday. Closed at weekends.
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