A home battery typically costs between £4,000 and £10,000 installed, depending on capacity, brand, inverter setup, and installation complexity. Before you spend that, you need to know whether it pays back, and over what timeframe. The answer depends on three things: whether you have solar panels, which electricity tariff you are on, and how much of your solar generation you currently export to the grid unused.
This article works through the numbers honestly. No sales pitch, no best-case projections. Just the figures you need to decide.
What a home battery actually does
A home battery stores electricity so you can use it at a different time from when it was generated or bought.
If you have solar panels, a battery stores the surplus generation that would otherwise be exported to the grid at a low export rate. You then use that stored energy in the evening or at night, avoiding buying electricity at the full retail price.
If you do not have solar panels, a battery charges from the grid at off-peak rates (typically at night) and discharges during the expensive peak hours in the morning and evening. The saving comes entirely from the price difference between those two periods.
Both approaches work. But the numbers are significantly better when solar panels are part of the system.
What a battery system costs
Prices vary by brand, capacity, and installation complexity. The figures below are for fully installed systems in the UK.
| Capacity | Typical installed cost | Best suited for |
|---|---|---|
| 5 kWh | £3,000 to £5,000 | 1 to 2 person household, low evening demand |
| 10 kWh | £4,500 to £9,500 | Family home, covers most of the evening and night |
| 15 kWh | £7,000 to £10,500 | Larger home or home with an EV |
Installation adds £500 to £1,500 depending on whether your inverter is already battery-ready. If you are adding a battery to an existing solar system, check the inverter compatibility first. Replacing an incompatible inverter adds £1,000 to £2,500 to the total.
With solar panels: where the savings come from
Most UK households with solar panels export 40 to 60% of their annual generation. Without a battery, that exported electricity earns a rate under the Smart Export Guarantee. Buying electricity back in the evening costs around 25p/kWh under current UK price-cap levels.
Your saving per unit stored is the difference between your import rate and the export rate you would otherwise receive. SEG rates vary widely: the best no-strings rates in 2026 are around 6p/kWh, while the highest rates (often requiring you to be an import customer with the same supplier) reach 15p or above. At 6p export and 25p import, the saving is 19p/kWh. At 15p export and 25p import, it is 10p/kWh. Check your actual export rate before running the numbers.
A typical 4 kWp solar system generates around 3,400 kWh per year in the UK. If 50% is exported (1,700 kWh), a battery lets you self-consume most of that instead.
- Extra self-consumption: 1,200 to 1,500 kWh per year (some export still makes sense)
- Saving per kWh: 10p to 19p depending on your export rate
- Annual saving from solar self-consumption: £120 to £285
Add tariff arbitrage if you are on an economy tariff. Charging the battery at 7p/kWh overnight and using that energy during peak periods at 25p/kWh adds a further saving of 18p per kWh cycled.
A 10 kWh battery cycling once per day at 18p/kWh arbitrage saves an additional £657 per year in theory. In practice, you will not fill and drain the battery every day at maximum efficiency. A realistic estimate for combined solar and tariff savings is £400 to £700 per year for a 10 kWh system.
Without solar panels: a harder case
Without solar, the only saving comes from buying cheap overnight electricity and avoiding expensive peak electricity. This requires a time-of-use tariff.
The price spread between off-peak and peak rates on tariffs like Octopus Agile or Economy 7 ranges from 10p to 25p/kWh depending on the day and season. A 10 kWh battery cycling once per day at a consistent 15p/kWh spread generates:
- 10 kWh x 15p x 365 days = £547 per year (theoretical maximum)
- Accounting for efficiency losses and non-ideal cycling: £300 to £450 per year
At £300 to £450 per year saving against a £7,000 to £10,000 battery, payback is 16 to 33 years. That approaches or exceeds the expected lifespan of most batteries, which is 10 to 15 years.
Without solar panels, a home battery is a difficult financial case. The technology works. The economics do not yet.
Payback period: what to expect
| Scenario | Annual saving | Battery cost £7,000 | Battery cost £10,000 |
|---|---|---|---|
| Solar, good tariff, low export rate | £600 to £800 | 9 to 12 years | 13 to 17 years |
| Solar, average tariff, higher export rate | £300 to £500 | 14 to 23 years | 20 to 33 years |
| No solar, time-of-use tariff | £300 to £450 | 16 to 23 years | 22 to 33 years |
| No solar, standard tariff | £50 to £150 | Not viable | Not viable |
These payback figures assume flat electricity prices. If retail electricity prices rise, payback periods shorten. If prices fall, they lengthen. The uncertainty cuts both ways. Use £7,000 as a cautious planning figure for a 10 kWh system today; some systems come in lower.
Common mistakes when buying a battery
Buying a battery before checking your inverter. Many older solar inverters are not battery-ready. Adding a compatible hybrid inverter to an existing system adds cost and complexity that some installers fail to mention upfront.
Choosing capacity based on solar panel output, not household demand. The right battery size matches your evening and overnight consumption, not your peak solar generation. A large solar array with a small household demand profile needs a modest battery, not a large one.
Assuming you will cycle the battery every day. In winter, a solar battery charges less because generation is low. In summer, it charges more. Annual average cycling is typically 250 to 300 full cycles per year in the UK, not 365.
Ignoring the tariff. A battery on a flat-rate tariff saves far less than one paired with a time-of-use tariff. Switching tariff at the same time as installing the battery is one of the highest-impact decisions you can make.
Expecting backup power by default. Most home batteries do not provide backup power during a grid outage unless you specifically buy a system with islanding capability. Check before you buy if backup power matters to you.
How to pick the right size
Start with your evening electricity consumption. Look at your smart meter data or energy bills and find your average usage between 4pm and 11pm. That figure, in kWh, is roughly the battery capacity you need.
For most UK households, that is 5 to 8 kWh. A 10 kWh battery gives you headroom for higher-demand days, an EV top-up, or overnight usage as well.
Going larger than 15 kWh rarely makes financial sense for a single-family home without a large EV fleet or very high energy consumption.
Calculate your home battery payback
Enter your solar generation, household consumption, and electricity tariff to get your personalised payback estimate.
Open Battery CalculatorShould you buy a battery now or wait?
Battery prices have fallen steadily for five years and are expected to continue falling. If your payback period is currently 18 years, waiting two to three years for prices to drop further is a rational choice.
The exception is if you are installing solar panels now. Adding a battery at the same time as solar reduces installation costs compared to adding it later, because the labour and electrical work overlaps. If the combined system has a payback under 15 years, doing both together makes sense.
Run the numbers for your specific situation before deciding. The Home Battery Backup Calculator takes your actual consumption and tariff and gives you a payback period based on your numbers, not industry averages.