Solar Battery Storage: Costs, Savings, and Whether It Is Worth It
The short answer
- Around £4,600 for a typical 5 kWh battery, in a range of £1,500 to £10,000
- About £180 a year added by a 5 kWh battery on a 4 kW solar system, once lost export income is counted
- About 26 years to pay back on solar alone, against a life of 10 to 12 years; better with a time of use tariff
A home battery costs £1,500 to £10,000, and the Energy Saving Trust puts a typical 5 kWh system at around £4,600. Added to a 4 kW solar array, a 5 kWh battery lifts the share of your own solar you use from about 19% to about 52%, which is worth about £180 a year once the export income you give up is counted. A battery lasts about 10 to 12 years, so on solar alone it rarely pays for itself before it needs replacing. The case is stronger with a time of use tariff, an electric car or a heat pump. This guide covers the costs, what a battery really adds, and when it makes sense.
Cost and savings by battery size
A 5 kWh battery costs around £4,600 and adds about £180 a year on a 4 kW system. Bigger batteries add little more: 10 kWh gives £217, as there is rarely enough surplus to fill them.
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The Energy Saving Trust says a home battery can cost anywhere from £1,500 to £10,000, that a 5 kWh system costs around £4,600, and that a typical home system might be 10 kWh. Fitting a battery at the same time as the panels can save money, because the installers are already on site. A typical unit is about 100cm by 60cm by 25cm: slightly taller and wider than a washing machine, but much less deep.
What a battery adds depends far more on how much spare solar there is to store than on its size. The table reads the MCS self-consumption tables for a 4 kW system in southern England and a household using 2,500 kWh a year that is out for about half the day.
| Battery | Usable capacity | Solar used at home | Extra benefit a year |
|---|---|---|---|
| No battery | None | 19% | None |
| 3 kWh battery | 2.7 kWh | 40% | £114 |
| 5 kWh battery | 4.5 kWh | 52% | £179 |
| 10 kWh battery | 9 kWh | 59% | £217 |
| 13 kWh battery | 11.7 kWh | 60% | £222 |
The data behind this table
Source: MCS MGD 003 Issue 2.0, table 7-12, generation 3,600 to 3,899 kWh. Usable capacity is 90% of the rated size, which MCS assumes for lithium batteries unless the datasheet says otherwise. Extra benefit is the extra solar used at home at 26.32p per kWh (Ofgem cap, October to December 2026) minus the 12p per kWh Outgoing Octopus export payment it replaces, on 3,780 kWh a year of generation.
Most of the gain comes from the first few kWh. Going from 5 kWh to 10 kWh adds only about £38 a year, because in winter there is rarely enough surplus to fill a big battery, and in summer a 5 kWh one already covers much of the evening's use. Use our solar panel calculator to model panels with and without a battery for your own roof and bill.
How batteries save money
Only by the gap between buying and exporting. Each stored kWh saves 26.32p minus your export rate, about 14p on a 12p tariff, so a 5 kWh battery is worth about £180 a year.
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Solar panels generate electricity during the day. Without a battery, any electricity you do not use at the time is exported to the grid on a Smart Export Guarantee tariff, which paid from 4.1p to 17.5p per kWh on the rates we checked on 25 September 2026, and 12p on Outgoing Octopus. With a battery, that surplus is stored and used in the evening, when you would otherwise buy from the grid at 26.32p per kWh.
So the saving on each kWh stored is the difference between the two: about 14p on a 12p export tariff, and anything from about 9p to 22p depending on your export rate. That is why a battery is worth less than it first looks. On the MCS figures, a 5 kWh battery moves about 1,250 kWh a year from export to use at home on a 4 kW system, which is worth about £180 a year.
With a time of use tariff, a battery can also charge from the grid at the cheap overnight rate and supply the house at peak times. That works in winter too, when solar output is low. The Energy Saving Trust says a battery saves more money running a heat pump alongside such a tariff than it does storing surplus solar. How much it adds depends on the gap between your tariff's cheap and peak rates, so check the rates on the tariff you would actually use. Our figures do not include it.
Payback: solar only vs solar plus battery
A battery roughly doubles payback on a flat rate tariff. A 4 kW system alone pays back in 10.8 years, and in 20.7 years with a 5 kWh battery, counting one £4,600 replacement.
| System | Cost | Benefit a year | Payback |
|---|---|---|---|
| 4 kW solar panels only | £6,000 | £556 | 10.8 years |
| 4 kW solar plus 5 kWh battery | £10,600, then £4,600 for a new battery | £735 | 20.7 years |
| The 5 kWh battery on its own | £4,600 | £179 | 25.7 years, against a 10 to 12 year life |
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The data behind this table
From our solar calculator: south facing roof in southern England, a household using 2,500 kWh a year that is out for about half the day, 12p export. Payback is cost divided by the first year's benefit. The combined system counts one replacement battery, because the first one wears out before the system has paid back. Over 25 years the panels alone return about £7,200 more than they cost, and panels with a battery about £2,200. A time of use tariff can improve the battery rows; we have not modelled it.
On a flat rate tariff, a battery roughly doubles the payback of a solar system. If a battery appeals for other reasons, the best-value order is usually panels first, then a battery later if your tariff or your electricity use changes. Read our solar panel payback guide for the full analysis without a battery.
0% VAT applies to batteries
Since 1 February 2024, batteries installed in homes qualify for the zero rate of VAT, including a battery retrofitted to existing solar panels, until 31 March 2027 (HMRC VAT Notice 708/6). From 1 April 2027 the rate becomes 5%, which would add about £230 to a £4,600 battery. Make sure your installer applies the correct rate.
When a battery is worth it
When you are out by day, or have a heat pump, electric car or time of use tariff. Out on weekdays, a battery adds about £185 a year on a 4 kW system, against £169 when home all day.
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You are out during the day. If nobody is home during the sunniest hours, most of your generation would be exported without a battery. A battery gains a little more here: on a 4 kW system it adds about £185 a year for a household that is out on weekdays, against about £169 for one that is home all day.
You have a heat pump. The Energy Saving Trust says a battery saves more money running a heat pump on a time of use tariff than it does storing surplus solar. Combined with a heat pump tariff, this is the strongest case for a battery.
You have or plan to get an electric vehicle. An electric car adds a large electricity demand that a battery and a cheap overnight rate can help to serve.
You are on a time of use tariff. Charging the battery when electricity is cheap and using it when it is expensive works all year round, including in winter when solar output is minimal.
You want backup power. Some battery systems can keep power running during a power cut and others cannot, so ask before you buy. This is an added benefit rather than a financial justification.
When a battery is not worth it
On a flat rate tariff you will not leave, or a tight budget. A £4,600 battery earning about £180 a year takes about 26 years to pay back, more than twice its expected life.
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You are home during the day. If you already use a good share of your solar as it is generated, a battery has less surplus to store and adds less.
You are on a flat rate tariff and will not switch. Without a time of use tariff, the savings from a battery come only from storing surplus solar. At about £180 a year, a £4,600 battery takes about 26 years to pay back, more than twice its expected life.
Your budget is tight. If you have to choose between more panels or a battery, more panels are usually the better investment. More generation means more self-consumption and more export income: a 6 kW system with no battery pays back in 11.6 years in our figures, against 20.7 years for 4 kW with a battery.
Battery lifespan and degradation
About 10 to 12 years, so it needs replacing before the panels. Panels last 25 years or more, and our payback figures price the replacement at today's £4,600.
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The Energy Saving Trust gives a typical battery lifespan of about 10 to 12 years. That is shorter than solar panels, which should last 25 years or more, so you will need to replace the battery before the panels. Warranties vary by make, so ask about the warranty on the battery and on its installation when you get quotes, as the Energy Saving Trust advises.
A battery system should never let the battery discharge completely, because that can significantly shorten its life. Most stop drawing on the battery at a set level, perhaps 20% of its capacity, and switch back to the grid. Our payback figures price a replacement battery at today's £4,600; if battery prices fall, the second battery will cost less.
Combining batteries with heat pumps
They pair well, especially with a time of use tariff. A heat pump in a 3 bed semi costs about £937 a year on a standard tariff or £666 on a heat pump tariff.
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A solar system with a battery pairs well with a heat pump. In summer, surplus solar can charge the battery for hot water in the evening. In winter, when the panels produce little, a time of use tariff can charge the battery overnight so the heat pump draws less at peak rates.
For scale, our model puts the running cost of a heat pump in an average 3 bed semi at about £937 a year on a standard tariff and about £666 on a heat pump tariff such as Cosy Octopus, about 18.7p per kWh with most heating in the cheap hours. Solar and a battery can bring that down further, by an amount that depends on the tariff and the home. Use our heat pump calculator and solar calculator to model this combination.
Frequently asked questions
How much does a solar battery cost?
The Energy Saving Trust puts home batteries at £1,500 to £10,000, with a 5 kWh system at around £4,600 and a typical home system at about 10 kWh. Batteries are zero rated for VAT until 31 March 2027.
Is a solar battery worth it?
Rarely on solar alone. On a 4 kW system a 5 kWh battery adds about £180 a year once lost export income is counted, so it takes about 26 years to pay back against a life of 10 to 12 years. It is more worthwhile with a time of use tariff, an electric car or a heat pump.
How long does a solar battery last?
About 10 to 12 years, according to the Energy Saving Trust, which is shorter than the 25 years or more that panels last. Over the life of the panels you should expect to buy a battery twice.
Can I add a battery to existing solar panels?
Yes. A battery can be retrofitted to an existing solar system, and a retrofitted battery also qualifies for 0% VAT until 31 March 2027. The Energy Saving Trust says fitting a battery at the same time as the panels can save money, because the installers are already on site.
How much does a solar battery save per year?
On a 4 kW system in southern England, a 5 kWh battery adds about £180 a year and a 10 kWh battery about £220, after the export income you give up. Charging from the grid on a cheap overnight tariff can add more, depending on the tariff.
Data sources
The Energy Saving Trust, MCS, Ofgem and PVGIS. Export rates come from Octopus Energy and E.ON Next, checked 25 September 2026, and VAT from HMRC.
Show every source
Battery cost, size and lifespan from the Energy Saving Trust battery storage advice, updated 19 August 2026. Self-use with and without a battery from MCS MGD 003. Electricity prices from the Ofgem price cap, October to December 2026. Solar generation from PVGIS, as used in our solar calculator. Export rates from Octopus Energy and E.ON Next, checked 25 September 2026. VAT from HMRC VAT Notice 708/6. Heat pump running costs from our shared heat model.