Solar Battery Storage: Costs, Savings, and Whether It Is Worth It
A home solar battery costs £2,500 to £6,000 and saves £200 to £550 per year depending on your usage pattern and tariff. Adding a battery to a solar panel system extends the payback by 2 to 4 years but increases your self-consumption of free solar electricity from roughly 40% to 70 to 80%. Combined with a time-of-use tariff, batteries can also store cheap overnight grid electricity for daytime use. This guide covers exact costs by battery size, realistic savings, when a battery makes sense, and when it does not.
Cost by battery size
| Battery capacity | Installed cost | Typical use case | Annual saving (with solar) |
|---|---|---|---|
| 3 to 4 kWh | £2,000 to £3,000 | Small household, 1-2 people | £150 to £250 |
| 5 to 6 kWh | £2,500 to £3,500 | Average household, 2-4 people | £200 to £350 |
| 8 to 10 kWh | £4,000 to £6,000 | Large household, heat pump, EV | £300 to £450 |
| 13 to 15 kWh | £5,500 to £8,000 | High consumption, full self-sufficiency goal | £350 to £550 |
Costs include battery unit and installation. Savings assume a 4 kW solar panel system and standard electricity at 24.5p/kWh. With time-of-use tariffs, savings increase by £100 to £200 per year.
For most UK households, a 5 to 6 kWh battery is the sweet spot. It stores enough to cover evening electricity use (cooking, lighting, entertainment) from solar generated during the day. Larger batteries are worth considering if you have a heat pump or electric vehicle that you want to charge from solar.
Use our solar panel calculator to model the combined return of panels plus battery for your property.
How batteries save money
Solar panels generate electricity during the day. Without a battery, any electricity you do not use immediately is exported to the grid at the Smart Export Guarantee rate (currently 4 to 15p/kWh depending on your supplier). With a battery, that surplus is stored and used in the evening when you would otherwise buy from the grid at 24.5p/kWh.
The saving per kWh stored is the difference between what you would have paid for grid electricity and what you would have earned by exporting. At current rates, that is roughly 10 to 20p per kWh stored. A 5 kWh battery cycling once per day saves 50p to £1 per day, or £180 to £365 per year.
With a time-of-use tariff like Octopus Agile or Cosy, the battery can also charge from the grid at cheap overnight rates (5 to 12p/kWh) and discharge during expensive peak periods (25 to 40p/kWh). This "grid arbitrage" adds an additional £100 to £200 per year in savings, even in winter when solar generation is low.
Payback: solar only vs solar plus battery
| System | Total cost | Annual saving | Payback |
|---|---|---|---|
| 4 kW solar panels only | £4,500 to £5,500 | £400 to £550 | 8 to 12 years |
| 4 kW solar plus 5 kWh battery | £7,000 to £9,000 | £600 to £900 | 10 to 14 years |
| 4 kW solar plus 5 kWh battery plus TOU tariff | £7,000 to £9,000 | £700 to £1,050 | 8 to 12 years |
Assumes south-facing roof in central England. Solar plus battery plus TOU tariff includes grid arbitrage savings. All systems qualify for 0% VAT until March 2027.
Without a time-of-use tariff, a battery extends payback by 2 to 4 years. With a TOU tariff, the battery pays for itself within the overall system payback because the additional savings from grid arbitrage offset the battery cost. Read our solar panel payback guide for the full analysis without a battery.
0% VAT applies to batteries
Solar batteries installed alongside or retrofitted to solar panels qualify for 0% VAT until March 2027. This saves £500 to £1,200 compared to the standard 20% rate. Make sure your installer applies the correct VAT rate.
When a battery is worth it
You work away from home during the day. If nobody is home during peak solar hours (10am to 4pm), most generated electricity would be exported without a battery. A battery stores it for when you return.
You have a heat pump. A battery charged from solar during the day can power your heat pump in the evening, further reducing running costs. Combined with a heat pump tariff, this is a powerful combination.
You have or plan to get an electric vehicle. Charging an EV from stored solar is significantly cheaper than charging from the grid during peak hours.
You are on a time-of-use tariff. Grid arbitrage (charge cheap, discharge expensive) makes batteries profitable even in winter when solar output is minimal.
You want backup power. Some batteries (such as the Tesla Powerwall) provide backup power during grid outages. This is an added benefit rather than a financial justification, but matters if you live in an area prone to power cuts.
When a battery is not worth it
You are home during the day. If you already use most of your solar generation in real time (working from home, electric cooking, running appliances during daylight), a battery adds cost without proportional benefit.
You are on a flat-rate tariff and will not switch. Without a TOU tariff, the savings from a battery come only from shifted self-consumption. The payback is 10 to 14 years, close to the battery's warranty period.
Your budget is tight. If you have to choose between bigger solar panels or a battery, bigger panels are usually the better investment. More generation means more self-consumption and more export income.
Battery lifespan and degradation
Modern lithium-ion batteries (the standard for home storage) are warranted for 10 years or 6,000 to 10,000 charge cycles. Most batteries cycle once per day, so a 10-year warranty covers 3,650 cycles, well within the rated limit.
After 10 years, the battery does not stop working. It gradually loses capacity, typically retaining 60 to 80% of its original capacity at warranty end. A 5 kWh battery might deliver 3 to 4 kWh after 10 years. Real-world lifespan is usually 12 to 15 years before performance drops to a level where replacement makes sense.
Battery prices are falling. By the time your first battery needs replacing, a new one will likely cost significantly less than what you paid originally.
Combining batteries with heat pumps
A solar panel system with battery storage pairs exceptionally well with a heat pump. During summer, surplus solar charges the battery, which powers the heat pump for hot water heating in the evening. During winter, a TOU tariff charges the battery overnight at 5 to 12p/kWh, and the battery supplements the heat pump during expensive peak hours.
A household with a 4 kW solar system, 10 kWh battery, and heat pump on an Agile tariff can achieve total energy costs (heating, hot water, electricity) under £800 per year for a well-insulated 3-bed semi. Use our heat pump calculator and solar calculator to model this combination.
Monitor your system performance with recommended energy monitors that show solar generation, battery charge, and grid import/export in real time. See recommended smart thermostats that can coordinate heat pump scheduling with battery charge levels.
Frequently asked questions
How much does a solar battery cost?
£2,500 to £6,000 depending on capacity. A 5 kWh battery (most common) costs £2,500 to £3,500 installed. 0% VAT applies until March 2027. Use our solar calculator for your setup.
Is a solar battery worth it?
Yes if you are out during the day, have a heat pump or EV, or use a time-of-use tariff. Less worth it if you are home during the day and already self-consume most solar output.
How long does a solar battery last?
10-year warranty, 12 to 15 year real-world lifespan. Retains 60 to 80% capacity at warranty end. Battery prices are falling, so replacement will be cheaper.
Can I add a battery to existing solar panels?
Yes. Requires a compatible inverter. Costs slightly more than installing together. Read Are Solar Panels Worth It? for the full system analysis.
How much does a solar battery save per year?
£200 to £350 from shifted self-consumption. £400 to £550 with a time-of-use tariff adding grid arbitrage. Depends on usage pattern and battery size.
Data sources
Battery costs from installer market data, March 2026. Electricity prices from Ofgem Q1 2026 price cap. Solar generation data from Energy Saving Trust. Export rates from Smart Export Guarantee supplier listings.