A 10kWh home battery costs from £5,336 installed in Octopus's published battery-only price (one Fox ESS EVO 10 or two Enphase IQ Battery 5P, April 2026), against an official median of £890 per kWh for 6 to 11 kWh batteries in 2025/26, about £8,900. Usable capacity varies by product from 8.76 kWh (Sigenergy BAT 10.0) to 10 kWh (two Enphase units). It runs an average home for around a day, and in this site's model saves about £414 a year with 4 kWp of solar on Octopus Flux in London.
Why 10kWh is the common choice
A family home using 3,000 to 4,000 kWh a year uses roughly 5 to 7 kWh a day outside daylight hours. A 10 kWh battery covers that with room to spare, fills from solar on most days from spring to autumn, and on a time-of-use tariff can be topped up cheaply in winter. It is large enough to earn every day and small enough to empty every day, and that balance is where a battery pays back fastest.
10kWh batteries compared
Five products are commonly quoted at about 10 kWh. They are not the same size once you look at the energy you can actually use, and their warranties promise very different things.
| Battery | Usable capacity | Battery warranty | Published UK price |
|---|---|---|---|
| Fox ESS EVO 10 (battery and hybrid inverter in one) | 10.24 kWh at 95% depth of discharge, about 9.7 kWh | 12 years at 70%, or 47.88 MWh, whichever first | From £5,336 installed (Octopus) |
| Two Enphase IQ Battery 5P (AC coupled) | 10.0 kWh | 15 years or 6,000 cycles at 60% | From £5,336 installed (Octopus) |
| Two myenergi libbi 5 kWh modules | 9.2 kWh (2 × 4.6) | 10 years, unlimited cycles when run by myenergi’s controller | Not published by the suppliers we checked |
| Two Sunsynk Elite modules | 9.2 kWh (2 × 4.6) | Cells 10 years or 6,000 cycles; BMS 5 years; general degradation excluded | From £3,995 per module installed (E.ON Next) |
| Sigenergy SigenStor BAT 10.0 | 8.76 kWh (9.04 kWh total) | 10 years at 60%, or 30.66 MWh (European terms, May 2025) | Not published by the suppliers we checked |
From manufacturers’ datasheets and warranty documents; prices as published by Octopus (April 2026 prices) and E.ON Next (read 6 October 2026).
The usable figures run from 8.76 kWh to 10 kWh, a difference of about 14% between batteries sold under the same label. On the same price, that is 14% more or less storage. The warranties differ more: Fox ESS promises 70% of capacity at year 12, Enphase and Sigenergy 60% at year 15 and 10 respectively, and Sunsynk’s terms list “degradation General cell life” as an exclusion, so they set no minimum capacity at all, although its own datasheet for one model quotes a warranty throughput of 16 MWh to 70% of capacity. If capacity at year ten matters to you, ask the installer to put the retention figure in writing.
What 10kWh costs
| Source | Price | What it covers |
|---|---|---|
| Octopus Energy | From £5,336 | One Fox ESS EVO 10 (10.24 kWh) or two Enphase IQ Battery 5P (10 kWh), battery only, installed (April 2026 prices) |
| Octopus Energy | £11,115 | 12 solar panels plus a 10 kWh battery, installed (Octopus labels this both April and July 2026 prices on the same page) |
| The Eco Experts | £8,500 to £10,000 | Its average installed range for 10 kWh (February 2026) |
| DESNZ official median | £890 per kWh | MCS-certified installs of 6 to 11 kWh, 2025/26: about £8,900 for 10 kWh |
Octopus’s battery-only price works out at about £521 per nominal kWh for a Fox ESS EVO 10, or about £550 per usable kWh; for two Enphase units it is about £534 per usable kWh. The official median is £890. The gap is the difference between a large supplier’s standard package and the whole market, including bespoke installations with backup hardware, consumer unit work or awkward locations.
The solar battery cost guide gives the average installation in each size band, and the cost per kWh delivered post works out what each kWh a 10 kWh battery hands back costs over ten years: 18.0p at Octopus’s £5,336 for a home with solar on Octopus Flux, in the model.
How long a 10kWh battery runs a house
| What is running | Roughly | 10 kWh lasts about |
|---|---|---|
| Essentials in a power cut (fridge, lights, router, boiler pump) | 0.3 to 0.5 kW | 20 to 30 hours |
| Average use for a 3,000 kWh home | 0.35 kW | 29 hours |
| A busy evening (cooking, TV, washing) | 1.5 to 2 kW | 5 to 6 hours |
| An electric shower | 7.5 to 10.5 kW | Minutes, if the inverter can supply it at all |
The inverter’s power rating limits what the battery can run at once, and a power cut only matters if the installation includes backup. See home battery backup.
Power as well as capacity
Two 10 kWh batteries can feel very different in use because of the inverter behind them. A Fox ESS EVO 10 comes in versions from 5 kW to 10 kW. Two Enphase units deliver 6.4 kVA together. A myenergi libbi system pairs its modules with a 3.68 kW or 5 kW hybrid inverter, and each Sigenergy BAT 10.0 module charges and discharges at up to 4.6 kW. Power also sets how fast the battery fills in a cheap window: at 3.68 kW, 10 kWh takes about 2 hours 45 minutes before losses, which fits inside Octopus Flux’s three cheap hours; at 5 kW, about two hours. Anything above 3.68 kW of combined inverter output on a single-phase home needs a G99 application before connection; G98 and G99 explained shows how each network operator handles it.
Filling it: solar in summer, tariffs in winter
PVGIS models a 4 kWp south-facing array in London at about 490 kWh in June, around 16 kWh a day, and about 145 kWh in December, under 5 kWh a day. In summer that fills a 10 kWh battery after covering the house. From November to February it does not, so a 10 kWh battery on a flat tariff sits partly empty for a third of the year. On Octopus Flux (which needs solar) or Agile, it charges cheaply from the grid instead and earns all year.
What it saves
This site’s model, for a home using 3,000 kWh a year with a 10 kWh battery:
| Set-up | Modelled saving a year |
|---|---|
| London, 4 kWp solar, Octopus Flux | £414 |
| Merseyside and North Wales, 4 kWp solar, Octopus Flux | £455 |
| London, 4 kWp solar, flat tariff | £174 |
| London, no solar, Agile Octopus | £335 |
At £5,336 and £414 a year, the simple payback is about 13 years; on a flat tariff it is over 30. The tariff decides whether a 10 kWh battery pays inside its warranty. The calculator runs your own region and usage.
Without solar the saving is smaller and steadier: £239 to £266 a year on 12 months of real Agile prices, set out in home battery without solar.
10kWh or a different size?
If your evening use is under about 5 kWh, a 5kWh battery may capture most of the saving for less; our analysis of what the second 5 kWh adds works through the trade-off tariff by tariff. If you have a heat pump, high evening use or plan to trade stored energy on Flux, look at three-module 15 kWh systems as well.
When comparing quotes, divide each price by the usable capacity it states, and compare the warranty’s retention figure and throughput cap, not just the years. Two “10 kWh” quotes can differ by more than a kilowatt-hour of usable energy. Compare several battery storage quotes on that basis before you choose.
At the other end, a 13kWh battery earns about £155 a year more than 10 kWh with solar on Octopus Flux for a 3,000 kWh home, and almost nothing more without solar. For the in-between size, the 12kWh battery page prices it against 10 and 13.5 kWh, and every size side by side is in one table.
Questions people ask
How long will a 10kWh battery last?
In hours, divide the usable energy by what the home is drawing. An average home using 3,000 kWh a year draws about 0.35 kW, so 10 kWh covers roughly 29 hours of average use, or an evening of cooking, TV and lights at 1.5 to 2 kW for five to six hours. In years, the warranties on 10 kWh products run from 10 to 15 years, promising 60% to 70% of capacity at the end, or no minimum at all in Sunsynk's case.
How much does a 10kWh battery cost?
Published installed prices start at £5,336 (Octopus, one Fox ESS EVO 10 or two Enphase IQ Battery 5P, battery only, April 2026 prices). The Eco Experts puts 10 kWh at £8,500 to £10,000. The official median for MCS-certified 6 to 11 kWh batteries was £890 per kWh in 2025/26, about £8,900 for 10 kWh.
Is a 10kWh battery 10kWh usable?
Not always. Two Enphase IQ Battery 5P units give 10.0 kWh usable. A Fox ESS EVO 10 holds 10.24 kWh with a 95% depth of discharge, about 9.7 kWh usable. Two myenergi libbi modules or two Sunsynk Elite modules give 9.2 kWh usable, and a Sigenergy SigenStor BAT 10.0 gives 8.76 kWh. Ask every installer for the usable figure.
Which 10kWh battery has the best warranty?
It depends what you value. Enphase runs longest, 15 years or 6,000 cycles, but promises only 60% of capacity. Fox ESS gives the EVO 10 12 years at 70%, up to 47.88 MWh. myenergi gives libbi 10 years with unlimited cycles when its own controller runs the system. Sunsynk's terms exclude general cell degradation, so they set no minimum capacity.
Is a 10kWh battery enough to run a house?
For a typical home using 2,700 to 4,000 kWh a year, it covers the evening and night on most days. It will not run high-power appliances such as an electric shower or an EV charger for long, and whether it runs anything in a power cut depends on the backup hardware installed.
How many solar panels does it take to charge a 10kWh battery?
On a sunny summer day, a 4 kWp array (about 10 panels) makes around 16 kWh in London in PVGIS's model, enough to run the house and fill a 10 kWh battery. In December the same array makes about 5 kWh a day, so in winter a 10 kWh battery relies on cheap-rate grid charging.