A solar battery stores the electricity your panels generate but your home is not using at that moment, then releases it later — usually in the evening, when the panels have gone quiet and you would otherwise be buying from the grid. That is the whole idea. The interesting questions are whether the economics stack up for your household, what one costs in 2026, and what the honest limits are. This guide answers those, with sources shown throughout.
The price gap that makes batteries interesting
Without a battery, every surplus unit your panels generate is exported. Under the Smart Export Guarantee, exporting households earned an average of 13p per kWh in 2024–25, according to Ofgem. Meanwhile, the average unit you buy back in the evening costs 26.11p under the July–September 2026 price cap.
That gap — roughly 13p on average tariffs — is the battery’s job. Each kilowatt-hour it catches at lunchtime and serves back at 8pm is a unit you did not sell cheap and buy back dear. Store around 1,500kWh a year and the arithmetic on those average rates is worth roughly £200; households with strong export tariffs will see less benefit per unit, households on poor ones more.
Said plainly: on export-versus-import arithmetic alone, a battery pays back slowly. The case strengthens considerably when you add the second lever below — which is why “do I need one?” has no universal answer, only a survey answer.
The second lever: cheap overnight electricity
Modern batteries are not restricted to solar charging. On a smart time-of-use tariff, a battery can fill up overnight, when some tariffs price units at a fraction of the peak rate, and run your home through the expensive morning and evening windows. In winter — when solar generation is at its lowest and your usage is at its highest — this is often what the battery spends most of its time doing.
This also means a battery can make sense without any solar panels at all, purely as a buy-low, use-high device. Standalone battery installations have qualified for 0% VAT since February 2024, the same treatment as batteries installed alongside panels.
How a home battery actually works
A few plain-English terms cover most of what you will see on a datasheet:
- Capacity (kWh) is how much electricity the battery holds. Home batteries typically range from around 5kWh to 13.5kWh, and larger systems stack multiple units.
- Usable capacity is the part you can actually draw on — batteries hold back a margin to protect their own health. Compare quotes on usable figures, not headline ones.
- Power (kW) is how fast it can charge or discharge. A battery with plenty of stored energy but a low power rating cannot run everything at once.
- DC-coupled vs AC-coupled: a DC-coupled battery shares a hybrid inverter with your panels — tidy and efficient when installed together. An AC-coupled battery has its own inverter and bolts onto any existing system, which is the usual route for retrofits.
Your installer notifies the local network operator about a battery just as with panels — smaller systems under the G98 process after commissioning, larger ones needing G99 approval first. That paperwork is the installer’s job, not yours.
What a battery costs in 2026
The Energy Saving Trust puts home battery costs in a range of roughly £1,500 to £10,000 installed, with a typical 5kWh system around £4,600. Price per kWh generally falls as capacity rises, and installing a battery at the same time as panels is cheaper than adding one later, because the scaffolding, electrician and commissioning visit are already part of the job.
The VAT position helps: residential battery storage in Great Britain is zero-rated until 31 March 2027 under HMRC’s VAT notice 708/6, after which the rate is due to revert to 5%.
How long batteries last — the honest version
Most lithium home batteries come with manufacturer warranties of around 10 years, with some models warranted to 12; warranties are also commonly capped by throughput or charge cycles, whichever comes first. Treat any talk of a battery lasting “a lifetime” as a red flag — no manufacturer warrants that, and we will not claim it either.
Two practical consequences follow. First, since solar panels are designed to last 25 to 30 years, a battery bought today may need replacing during the panels’ life — sensible planning includes that. Second, the warranty document matters more than the brochure: check the years, the throughput cap, and what percentage of original capacity the manufacturer guarantees at the end of the term.
What a battery will not do
- It will not take your bill to zero. Standing charges apply every day, and winter demand outruns winter generation in every UK home we have ever surveyed.
- It is not automatically a backup supply. Many installations shut down in a power cut, as the grid connection rules require, unless the system is specifically designed with backup capability. If keeping the lights on through outages matters to you, say so at the survey stage — it changes the specification.
- It cannot fix an undersized solar array. A battery stores surplus; if your panels rarely generate one, there is little to store. Sizing the two together is the point of doing the sums properly.
Sizing: matching the battery to your evenings
Ofgem’s typical household electricity figure is now 2,500kWh a year — call it 7kWh a day on average, weighted towards mornings and evenings. A battery sized close to your typical evening consumption, and to the surplus your panels actually produce, does the most work per pound. One sized far beyond either spends its life half empty.
This is exactly what a proper survey calculates: your usage pattern from real bills, your roof’s generation, and the battery capacity that bridges the two without waste. Our battery storage page covers the systems we install, and if you are starting from scratch our solar panels guide explains the generation side. Households with an electric car should look at EV charging alongside — a car is, in effect, the biggest battery you own. And if you are reading from an off-gas village, our note on battery storage in Hampshire explains why the case is often strongest where mains gas never arrived.
Questions worth asking any installer
- What is the usable capacity, and what does the warranty guarantee at end of term?
- Is the quote DC-coupled or AC-coupled, and why is that right for my system?
- Does it include the G98 or G99 network paperwork?
- Will the system provide backup in a power cut — and if not, what would that cost?
- What happens to my export payments once the battery is keeping more power at home?
An installer comfortable answering those in writing is an installer taking your money seriously.
Thinking about storage?
Whether a battery earns its keep in your home is a question of tariffs, usage and roof output — three things we can put real numbers on in one visit. Request a free, no-obligation survey through our contact page and we will show you the arithmetic, battery included and battery excluded, so you can decide with the figures in front of you. No pressure, just clear advice.