Solar battery cost by size: 5, 10 or 13.5 kWh?
What a 6 kWp solar system costs in the UK with no battery, or a 5, 10 or 13.5 kWh battery, at 0% VAT until March 2027, and how to size storage to your use.
A 6 kWp solar panel system with a 5 kWh battery typically costs £12,500 in the UK, installed and at 0% VAT. Stepping up to a 10 kWh battery brings it to about £15,500, and a 13.5 kWh battery to around £17,600. The same panels with no battery at all are about £9,500. Installing solar panels and batteries is charged at 0% VAT until 31 March 2027, and all our figures use that rate.
The same system, four battery sizes
Every row below is the same 6 kWp system on a pitched tiled roof - panels, mounting, inverter, cabling, monitoring, scaffolding and commissioning - changing only the battery.
| Material | Typical | Usual range | Lifespan |
|---|---|---|---|
| No battery | £9,500 | £7,400 – £12,300 | – |
| 5 kWh battery | £12,500 | £9,750 – £16,200 | – |
| 10 kWh battery | £15,500 | £12,100 – £20,100 | – |
| 13.5 kWh battery | £17,600 | £13,700 – £22,900 | – |
Because everything else stays the same, the gap between two rows is what the extra storage costs you. Change the system size and see every line in our Solar panels.
What each size suits
No battery
Panels only are the cheapest way into solar (£9,500) and deliver most of the saving if someone is at home in the day to use the power as it is generated. Anything you do not use is exported.
5 kWh
A 5 kWh battery (£12,500) covers a typical household's evening: lighting, cooking, TV and the fridge through to bedtime. It is the size that most often pays its way for a family out at work during the day.
10 kWh
A 10 kWh battery (£15,500) suits larger homes with higher evening use, or households on a time-of-use tariff that want to charge cheaply overnight in winter, when the panels produce little, and run the house on stored power through the dearer hours.
13.5 kWh
A 13.5 kWh battery (£17,600) makes sense with a heat pump, an electric car or very high evening use. With a 6 kWp array it will rarely fill from solar alone in winter, so it relies on cheap overnight charging to earn its keep.
Size to your evening use, not your panels
The most common mistake is buying the biggest battery the installer offers. A battery only saves money on the power that actually passes through it. An oversized battery sits half-empty most of the year and takes much longer to pay back.
A simple way to size it:
- Look at your bills or smart meter data and estimate how much you use from late afternoon until the next morning.
- Aim for a battery that covers most of that on a typical day, not the worst winter day.
- Add capacity only for a specific reason: a heat pump, an electric car charged at home or a time-of-use tariff you will actually use.
What the price includes
- Scaffolding put up, hired for the job and taken down
- 450 W monocrystalline all-black panels, enough for about 6 kWp
- Mounting rails fixed with roof hooks under the tiles
- A hybrid inverter that manages panels and battery, with isolation and surge protection
- Cabling to the consumer unit with a dedicated breaker
- Monitoring of generation, battery and household use
- Permanent roof anchor points, connection and commissioning
Not included: roof repairs under the array, a new consumer unit if yours has no spare way, a three-phase supply upgrade, and fees or paperwork with your network operator.
We build these prices from the equipment and the hours it takes to install at local labour rates, and check them against market prices and real quotes. Scaffolding, the inverter and the electrical work cost much the same whichever battery you choose, which is why the price does not double when the battery does.
Adding a battery later
You can fit a battery later, but it usually costs more: a panels-only system has a standard inverter, so a later battery needs its own inverter or a swap to a hybrid one, and you pay for electrical work twice. There is also the deadline: a battery installed as part of the job before 31 March 2027 gets 0% VAT; one added after it may not.
Rules and other help
- Electrical work. Connecting panels and batteries is notifiable in England and Wales: it must be done by a registered electrician (Part P) or notified to building control. Keep the certificate.
- Warm Homes Plan. Published in January 2026, it commits £15bn to 2030, including grants for low-income households and low- or zero-interest loans being phased in.
Check your quote
Ask every installer to quote the same panel wattage with two battery sizes, and to name the battery's usable capacity, not just its headline size. Then compare each total with typical prices where you live using our "Is my quote fair?" tool: Is my quote fair?.