Guide · The three batteries we fit
Written by our MCS-accredited installers, who fit all three · Updated October 2026
Short answer
Fox ESS for the lowest price, Sigenergy if an EV charger or heat pump is next, Powerwall 3 for the biggest single battery.
We fit all three, so we have no reason to push one — each earns its place in a different kind of home.
Which one is you?
Fox ESS EP12
The most storage for the money, and the battery we fit most.
Sigenergy SigenStor
Battery, EV charger and heat pump, built as one system.
Tesla Powerwall 3
The biggest single battery we fit, with whole-house power.
Smaller home? The Fox ESS EP6 (5.76 kWh) is from £1,990 battery only, or from £3,290 with a new inverter. See every battery price →
All prices fitted, 0% VAT. All three carry a 10-year warranty. Your exact price is fixed after a free survey — it depends on where the battery goes, the cable run and your consumer unit. The price we quote is the price you pay. Prices checked 7 October 2026.
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For most homes, yes. It's the brand we install most, because you get a lot of storage for your money.
The hybrid inverter (the box that runs your panels and battery) and the battery pair cleanly. The app is straightforward.
Best for: the most storage per pound. Honestly, that's most homes.
Because it grows with you. The SigenStor stacks battery modules like building blocks.
You start at 8.76 kWh and add modules later, to 17.5 kWh, 26 kWh or beyond. It is a five-in-one unit: the inverter and battery sit together, ready for EV charging.
It looks tidy on a wall, and the app is excellent.
Best for: homes that will need more storage later — an EV on the way, a heat pump planned — and anyone who values room to expand.
It is if you want one premium brand for everything, or you drive a Tesla — the car and battery work together seamlessly.
One unit holds 13.5 kWh and a built-in solar inverter. Its app is the slickest in the business.
You do pay a premium for the badge and the polish. Capacity also comes in fixed 13.5 kWh steps, one whole unit at a time, rather than small modules.
Best for: Tesla households, and anyone who wants the premium, single-brand experience. Our full Tesla Powerwall 3 review →
The things customers ask us to compare, and what each costs with solar panels.
| Feature | Fox ESS | Sigenergy | Powerwall 3 |
|---|---|---|---|
| Value per kWh | Leads | Close behind | At a premium |
| Adding more later | Add another unit | Leads — add a module | Add another 13.5 kWh unit |
| App and ecosystem | Perfectly capable | Strong | Leads |
| Warranty | 10 years on all three, plus our insurance-backed workmanship guarantee | ||
| With solar panels | 10 panels + 11.52 kWh from £7,990 15–20 panels + 23 kWh from £13,400 |
12 panels + 8.8 kWh from £11,990 15 panels + 17.5 kWh (two batteries) from £13,990 |
Priced with your free roof design |
Package prices are for panels on one roof face with a single scaffold lift, at 0% VAT. Extra roof faces or scaffolding are quoted at the survey.
Think about how your home will use electricity in a few years, not just today. Most homes want the most storage per pound, which is why Fox ESS is the one we fit most.
Battery costs in detail → or get your free roof design and fixed price.
Yes. Here are two of ours, each written up in full.
Fox ESS. An EP6 (5.76 kWh) added to the hybrid inverter you already have is from £1,990, and an EP12 (11.52 kWh) is from £2,790. A Sigenergy SigenStor (8.76 kWh) is from £3,190. A Powerwall 3 with its built-in inverter is from £6,390. All fitted, 0% VAT.
The Powerwall 3. It holds 13.5 kWh in one unit, the biggest single battery we fit, and gives up to 11.04 kW at once — enough to run the whole house. A Fox ESS EP12 holds 11.52 kWh and a Sigenergy module 8.76 kWh, and both stack for more.
Sigenergy, if you want your battery, EV charger and heat pump built as one system. Fox ESS works with an EV charger too — we fit Fox ESS chargers, and they run from the same FoxCloud app as the battery. If you drive a Tesla, the Powerwall 3 works seamlessly with the car.
Yes, with all three. Sigenergy adds another module to the stack. Fox ESS adds another unit: two EP12s make 23 kWh, three make 34.5 kWh. The Powerwall 3 grows in 13.5 kWh steps, up to seven units (94.5 kWh). We plan for it in your design, so adding one later is simple.
The Powerwall 3. Its up to 11.04 kW can run most of your home, not just the lights and the fridge. Backup needs Tesla's Backup Gateway 2, which is its own line on your quote. Fox ESS supports backup too, but whole-house power-cut cover is not its strength.
10 years on all three, plus our insurance-backed workmanship guarantee. Tesla also guarantees the Powerwall 3 still holds at least 80% of its 13.5 kWh at year 10, as long as it stays connected to the internet.
Yes. We add batteries to solar systems other firms fitted. Battery-only prices are for joining the hybrid inverter you already have. If yours can't take a battery, we fit a new inverter with it. A Powerwall 3 can take over from an old solar inverter at the same time.
Everything in this guide is fitted by our own team across Essex, Herts, Beds, Bucks and Kent — a company owner on every install.
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