What a home battery does
How a solar battery cuts your bills.
A home battery does up to three jobs. Which ones you need decides its size, the tariff that suits it and whether to add backup.
Keeps your solar for the evening
Without a battery, much of what your panels make in the day goes to the grid for about 12p a unit. A battery holds on to it for the evening, when you'd otherwise be buying electricity at more than twice that.
Fills up cheap overnight
On a time-of-use tariff, electricity can drop to about 7p a unit overnight. The battery charges then and runs the house through the expensive evening hours, with or without solar.
Keeps the lights on in a power cut
With backup added, the battery takes over when the grid goes down: one socket for the essentials, or the whole house. How backup works
Barns and workshops with no grid connection can run on solar and batteries alone. Those are designed per site: see commercial and farm solar.
Which battery?
What size solar battery do you need?
Three questions. It suggests the battery and what it costs fitted, and shows the saving where we can work it out honestly.
A 5.2kWh battery
Fox ESS EP6, fitted the same days as your panels
Estimated for a roof facing an unknown direction, with someone home some of the day. Includes charging overnight at about 7p when the sun can't fill the battery. That needs a time-of-use tariff; on a flat rate it pays back more slowly.
Get my written estimateSolar battery cost
Solar battery prices, fitted in Somerset.
Cheapest fitted the same days as new panels. A battery on its own works with the solar you've got, or with none at all. Panels too? See the full solar panel and battery price list.
| Battery | Usable | Price |
|---|---|---|
| With new panelsFox ESS EP6 | +£1,400 | |
| With new panelsFox ESS EP12 | +£2,450 | |
| On its own, or added to existing solarAbout 10kWh, with its own 3.68kW battery inverter | from £4,250 | |
| Bigger batteryFor bigger homes, a heat pump or electric heating | from £6,750 |
Every battery includes
- A free survey before the price is fixed
- The G98 or G99 paperwork with the network operator
- Fitting and testing by our NICEIC-approved team
- The app set up on your phone, and a walk-through before we leave
- An Electrical Installation Certificate for the work
- Deposit protection and an insurance-backed guarantee through QANW
Home batteries are zero-rated for VAT until 31 March 2027, already reflected above. If your consumer unit or supply needs upgrading first, we'll say so at the survey and price it separately.
Already got solar?
Add a battery to your existing solar panels.
You don't need to touch the panels already on your roof, whoever fitted them.
- We fit a separate battery with its own inverter, wired into your consumer unit, so it works alongside any system, including older Feed-in Tariff installs.
- Your Feed-in Tariff payments carry on. We don't touch your generation meter, and we'll tell you what to let your supplier know.
- On its own, a 3.68kW battery inverter only needs a G98 notification once it's fitted. Added to existing solar, the two together can need a G99 application or an export limit. We check that at the survey and deal with it either way.
Panels or inverter playing up as well? See repairs and aftercare.
Battery backup
What stays on in a power cut.
A battery on its own switches off in a power cut, just like solar panels do. Backup has to be added, and there are two levels of it.
No backupStandard on every battery
Everything goes off, even with a full battery. It's a safety rule: the battery shuts down with the grid so nobody working on the cables outside gets a shock from your house. It comes back on by itself when the power returns.
IncludedBackup socketOne dedicated socket
A single socket stays live from the battery. Plug in the fridge-freezer and the router and they'll keep going for many hours. Everything else goes off.
+£250Whole-home backupAutomatic changeover
A gateway disconnects the house from the grid and the battery runs the lot: lights, sockets and the boiler. It all shares the inverter's output, so the kettle, oven and shower at once will be too much.
from £850How quickly it switches over depends on the make, from a split second to a few seconds. Working from home on a desktop computer? Tell us and we'll pick kit to suit.
Still on when the street isn't
44 panels, 21.1kWp, on an EcoFlow 15kW three-phase inverter, with 10kWh of storage wired to keep the site running in a power cut, rather than tripping out with the grid.
Where it goes
Where a home battery can go, and where it can't.
These rules come from PAS 63100, the fire safety standard for home batteries, and we follow it on every install.
Good places
- Outside on a wall, at least a metre from doors, windows, vents and escape routes
- A garage or outbuilding, with a guard if a car could hit it
- A utility room with fire-resistant walls, ventilation to the outside and a linked smoke alarm
Never
- Lofts and roof spaces
- Bedrooms, or cupboards that open into one
- Hallways, landings and stairs, because they're your way out in a fire
- Cellars with no outside access
- Within 2 metres of an oil tank or anything else flammable
About the size of a washing machine
| Unit | Storage | Width × height |
|---|---|---|
| Washing machine, for scale | 600 × 850mm | |
| Fox ESS EP12 | 10.4kWh | 710 × 640mm, plus the inverter |
| Fox ESS PowerQ | 8.9kWh | 570 × about 800mm |
| EcoFlow | 10kWh | 680 × about 940mm |
| Sigenergy | 8.8kWh | about 770 × 600mm |
Depths run from about 200 to 380mm depending on the make. We measure up properly at the survey.
The batteries we fit
Fox ESS, EcoFlow, Sigenergy and Tesla batteries.
Four makes, set up properly by our own electricians and looked after if anything goes wrong. Happy to price them side by side.
Fox ESSEP6, EP12 and PowerQ
The best value per kWh we fit, and what our list prices are based on, with a 10-year warranty. Rated for open weather, so it can go outside without shelter.
EcoFlowStacked 5kWh modules
Our electricians' favourite to fit, with a 15-year warranty. A slim, tidy tower with an app that's easy to live with. Up to six modules on one inverter, about 30kWh. Its hybrid inverter takes solar panels later. Needs a sheltered spot if it goes outside. Costs a little more.
SigenergyStacked modules
Rated for open weather, like Fox ESS. Costs a little more.
Tesla Powerwall13.5kWh per unit
We're registered and approved to fit it. One wall-mounted unit that can go outside. It isn't on our price list, so we price it in your written estimate.
Fair questions
Solar battery questions.
Do I need solar panels to have a battery?
No. On a time-of-use tariff the battery charges overnight at the cheap rate and runs the expensive evening hours. With solar it does both jobs.
What size battery do I need?
We size it to your evenings, not your whole day. For most homes that's 5.2 or 10.4kWh. A bigger home, a heat pump or electric heating can justify about 20kWh. An electric car doesn't change it: the car charges straight from the grid overnight.
How long do solar batteries last?
Fox ESS batteries carry a 10-year warranty and EcoFlow 15 years. A battery doesn't stop when the warranty ends; it slowly holds a little less charge each year, and the warranty guarantees how much it keeps.
Do you fit Tesla Powerwall?
Yes, we're registered and approved to fit it. Ask for it in your estimate request and we'll price it alongside the batteries above.
Can you add a battery to my existing solar?
Yes, from £4,250 for about 10kWh, with its own inverter so your panels and any Feed-in Tariff payments are left as they are.
Will a battery keep my power on in a power cut?
Only with backup added. A backup socket is £250 extra; whole-home backup is from £850. Without either, the battery switches off with the grid.
Does the battery charge my electric car?
Not usually. The car charges straight from the grid on your cheap overnight rate. The battery is there for the house, so we size it for the house.
Where does it go?
Outside on a wall, in a garage or in a suitable utility room. Never in a loft, a bedroom or on your way out of the house in a fire.
Is a battery worth it?
If you're getting panels, the chooser above shows what the battery adds and how long it takes to pay for itself. With solar already, or none, the saving depends on your tariff and system, so we work it out in your written estimate.
Do you fit batteries across Somerset?
Yes: Wells, Glastonbury, Frome, Bridgwater, Yeovil, Taunton and Bath. The price is fixed in writing once the survey's done.
Catch a few rays
Your battery, sized in writing, in two working days.
A written estimate for your home: the battery we'd suggest, a guide price and what it saves. No visit needed. One check-in after a week, then it's your call.
Rather talk it through? 0117 473 0300