A home battery is worth it when you can fill it cheaply and empty it every day: from solar you would otherwise export for 5 to 15p per kWh, or from a cheap overnight rate on a time of use tariff. A 10 kWh battery costs £4,500 to £7,000 installed at 0% VAT and lasts around 10 years or 6,000 cycles, so it needs to save several hundred pounds a year to pay back inside its life. That happens for homes with solar and an EV or heat pump, or a good overnight tariff; it does not happen for a low use home on a flat tariff.
Key takeaways
- A battery pays when it cycles most days. Solar surplus in summer plus a cheap overnight tariff in winter is the combination that works.
- Typical installed prices: 5 kWh £3,000 to £4,500; 10 kWh £4,500 to £7,000; 13.5 kWh £6,000 to £8,500. All 0% VAT until 31 March 2027, including a battery fitted on its own.
- Lifespan around 10 years or 6,000 cycles, whichever comes first, so payback has to land inside that.
- Without solar, the saving is the gap between your peak and off-peak rate multiplied by the kWh you shift each day. With solar, add the gap between your import price and the export price you give up.
- An EV, a heat pump or electric cooking raises daily use and improves the case; a small flat with low use rarely justifies one.
- Batteries are arranged by Stay Warm and installed by accredited, MCS certified installers, usually in a garage, utility room, or on an outside wall.
Is a home battery worth it?
It depends on one thing: how many kWh you can push through it each day at a good price difference. A battery earns money every time it charges cheap and discharges when electricity is dear. If it sits half full most days, it earns little and the money was better spent on insulation or panels.
| Your situation | Battery worth it? | Why |
|---|---|---|
| Solar panels, home in the day, low evening use | Marginal | Little surplus to store; you use the solar as it comes |
| Solar panels, out in the day, evening use | Usually yes | Daytime export at 5 to 15p becomes evening use at full import price |
| Solar plus EV or heat pump | Yes | High daily use, the battery cycles fully most days |
| No solar, time of use tariff, EV or heat pump | Often yes | Charge overnight at the cheap rate, run the house on it by day |
| No solar, flat tariff | No | Nothing cheap to fill it with |
| Small flat, low use, moving in a few years | No | Too few kWh a day and too short a horizon |
A battery with solar panels
A south facing 4 kW system in London generates around 3,400 to 3,800 kWh a year, most of it between 10am and 4pm. If nobody is home, most of that is exported under the Smart Export Guarantee at 5 to 15p per kWh, and bought back in the evening at the full import rate. A battery keeps the surplus for the evening. The saving per stored kWh is your import price minus the export price you give up.
As an illustration only: if you store 1,500 kWh of surplus a year and the gap between import and export prices is 10 to 20p, the battery saves £150 to £300 a year from solar alone. That does not pay back a £5,000 battery inside ten years on its own. What makes it work is adding winter overnight charging on a time of use tariff, and higher daily use from an EV or heat pump. See are solar panels worth it.
A battery without solar: time of use tariffs
Since 1 February 2024 a battery fitted on its own, with no solar, has been 0% VAT, and the case for it rests entirely on the tariff. Time of use tariffs give a cheap rate for a few hours overnight and a dearer rate by day. The battery charges at night and runs the house during the day and evening. Some tariffs are built for EV owners, some for heat pump owners, and the cheap window and rates vary by supplier.
The sum, again as an illustration: a 10 kWh battery cycling 8 kWh a day at a 15 to 20p gap between the overnight and daytime rates saves £1.20 to £1.60 a day, about £440 to £580 a year. Against a £5,500 battery that is a payback of roughly 9 to 12 years, close to the 10 year or 6,000 cycle life. A bigger gap, a larger daily use or a lower battery price shortens it. A flat tariff removes it altogether. Put your own rates into the sum before you buy.
What size battery do I need and what does it cost?
Size the battery to your evening and overnight use, not to your solar system. A typical home uses around 2,700 kWh a year, about 7 to 8 kWh a day, of which perhaps half falls outside daylight hours. An EV or heat pump can double that. Typical installed prices, 0% VAT:
| Usable capacity | Typical installed cost | Suits |
|---|---|---|
| 5 kWh | £3,000 to £4,500 | Small home, low evening use, solar surplus only |
| 10 kWh | £4,500 to £7,000 | Typical 3 bed home, solar plus overnight charging |
| 13.5 kWh | £6,000 to £8,500 | Home with an EV or heat pump, high daily use |
Modular systems let you add capacity later, so start with what you can cycle fully. Fitting solar and battery together is cheaper than adding a battery later because they can share one hybrid inverter.
How long does a home battery last?
Around 10 years or 6,000 cycles, whichever comes first. One full cycle a day is 365 a year, so a battery cycled daily reaches both limits at about the same time. Capacity fades gradually rather than failing outright. Check the warranty covers cycles as well as years, and that it is backed by the manufacturer, not only the installer.
Where does the battery go and who fits it?
- Location. A garage, utility room, under stairs cupboard or an outside wall. Lofts are usually avoided because of summer heat, weight on the joists and access. It needs a cool, dry spot with clear space around it.
- Electrical work. A connection to the consumer unit, sometimes a consumer unit upgrade, and a notification to the electricity network operator, which the installer handles.
- Installer. Batteries are arranged and project-managed by Stay Warm and installed by accredited, MCS certified installers. MCS certification is what makes the system eligible for the Smart Export Guarantee if solar is fitted with it.
- VAT. 0% until 31 March 2027, then 5%, whether fitted with solar or alone.
Low income households in an EPC D to G home may be able to get solar and a battery through their council under the Warm Homes: Local Grant, where the council appoints the installer; see the solar panel grants guide. For everyone else, the battery storage service page explains how we arrange it, starting with a free survey of your use and your roof.
Frequently asked questions
How much does a home battery cost in the UK?
Typically £3,000 to £4,500 for 5 kWh, £4,500 to £7,000 for 10 kWh and £6,000 to £8,500 for 13.5 kWh, installed, at 0% VAT until 31 March 2027. Fitting a battery at the same time as solar is cheaper than adding one later because they share an inverter.
Is a battery worth it without solar panels?
Only on a time of use tariff. The battery charges overnight at the cheap rate and runs the house by day. If the gap between the rates is large and you use 8 kWh or more a day, payback can land inside the battery's life. On a flat tariff there is nothing cheap to store, so no.
How long does a home battery take to pay back?
It depends on your tariff gap and daily use. As an illustration, a £5,500 10 kWh battery cycling 8 kWh a day at a 15 to 20p gap saves about £440 to £580 a year, a payback of roughly 9 to 12 years. Solar surplus, an EV or a heat pump shortens that.
Do I pay VAT on a home battery?
No. Battery storage is an energy-saving material under HMRC VAT Notice 708/6, at 0% VAT until 31 March 2027, then 5%. Since 1 February 2024 that includes a battery installed on its own, without solar.
Does a battery keep the lights on in a power cut?
Only if it is set up with a backup function, which not every system has and which adds cost. Most standard installations switch off in a power cut for the safety of network engineers. Ask for it at quote stage if it matters to you.