The short answer: a 4 kW solar panel system with a 5 kWh battery costs about £9,000 to £12,500 installed. The battery itself adds roughly £2,500 to £5,000 when it is fitted at the same time as the panels.
Solar and battery prices by system size
| Solar system | Solar only | With a 5 kWh battery | With a 10 kWh battery |
|---|---|---|---|
| 3 kW | £5,000 to £6,000 | £8,000 to £10,000 | Rarely needed |
| 4 kW | £6,000 to £8,000 | £9,000 to £12,500 | £10,500 to £16,000 |
| 5 kW | £7,000 to £9,000 | £10,000 to £13,500 | £11,500 to £17,000 |
| 6 kW | £8,000 to £11,000 | £11,500 to £15,000 | £12,500 to £19,000 |
A 5 kWh battery typically adds £2,500 to £5,000 and a 10 kWh battery £4,500 to £8,000. There is no VAT on batteries until 31 March 2027.
Is a battery worth the extra money?
It depends on what you use it for, and this is where many sales pitches are too optimistic.
Storing your own solar power. Without a battery, spare solar power is exported and you are paid for it, typically around 15p per kWh on a good tariff. With a battery, you keep that power and avoid buying it later at about 26p. So each stored unit gains you about 11p, not 26p. A 5 kWh battery that fills and empties around 250 times a year would gain roughly £140 a year. On a £3,500 battery, that alone is a very long payback.
Charging on cheap overnight electricity. This is where batteries earn their keep. On a time-of-use tariff, you can fill the battery overnight at around 7.5p per kWh and use it during the day in place of power at 26p. A 5 kWh battery cycled daily this way could save around £340 a year, a payback of roughly ten years.
In practice most households do both: solar fills the battery in summer and cheap overnight power fills it in winter.
These are our own calculations from current prices. Your result will depend on your tariff and how much electricity you use in the evening.
When a battery makes most sense
- You are out during the day and use most of your electricity in the evening.
- You are willing to switch to a time-of-use tariff.
- You have, or plan to get, a heat pump or electric car.
- Your export rate is low.
When to skip it, or add it later
- You are home in the day and already use most of your solar power.
- You are on a high export tariff.
- The budget is tight: panels alone pay back faster.
If you might add a battery later, ask for a hybrid inverter now. Retrofitting usually costs more than installing everything together.
Paying for it
The Warm Homes Loan Scheme allows up to £15,000 for solar and a further £15,000 for a battery. See how the loan works.
Frequently asked questions
What size battery do I need?
Most homes with a 4 to 5 kW system choose 5 to 10 kWh. Bigger batteries suit homes with high evening use, an electric car or a heat pump.
Can I add a battery to existing solar panels?
Yes, although it usually costs more than fitting it with the panels.
How long do solar batteries last?
Most come with a ten-year warranty. Check the warranty covers a stated capacity at the end of the period.
Sources
Correct at the time of publication, 12 November 2026.
- Ofgem, energy price cap unit rates: https://www.ofgem.gov.uk/your-energy-supply/your-energy-bill/energy-price-cap-unit-rates-and-standing-charges
- HMRC, VAT rates on energy-saving materials, including batteries: https://www.gov.uk/guidance/vat-rates-on-different-goods-and-services
- GOV.UK, Warm Homes Loan Scheme: https://www.gov.uk/warm-homes-loan-scheme
- Battery and package prices are drawn from published UK price guides, including OVO (https://solar-and-heating.ovo.com/blog/solar-panel-and-battery-cost-uk). The 10 kWh package column and all payback figures are our own calculations.