Buy your electricity at night. Use it through the day.
A home battery charges while electricity is cheap and runs the house when it is expensive. Nothing goes on your roof.
Check my savingsCharging at 8pRunning the house, avoiding 26.32p
Illustrative figures. All figures on this page are worked examples. Installed prices for the launch sizes are being confirmed with our installer partners; your recommendation gives your own figure.
Saved in the first year, for a home spending £350 a month with an electric car and a hot tub
£690 of that comes from moving the car and the hot tub onto a cheap overnight rate, which needs no battery. The 30 kWh battery adds £1,713. Installed price £12,500 including VAT, paid back in 5.2 years. Flat rate 26.32p, overnight 8p, daytime 28p, prices at 1 October 2026, with 10% taken off the saving for caution. Electricity carries no VAT until 31 March 2027; the flat rate is roughly 5% higher from April. Worked example; your own figure comes from your bill.
The mechanism
How buying at night and using by day works
Electricity costs different amounts at different times. On a time-of-use tariff, overnight units cost a fraction of the daytime price. A battery charges during that cheap window and then runs the house through the expensive hours, so the meter records very little at the high rate.
The cheap window also decides the size. A 3.68 kW inverter fills a 20 kWh battery in six hours and can be fitted without waiting for the network operator. A 30 kWh battery needs a bigger inverter and the operator's approval first. Your estimate works out both.
The difference from solar
Nothing goes on your roof
There are no panels and no scaffolding, and a battery inside or against the house does not normally need planning permission. The work is a battery and an inverter installed inside or against the house. It takes one and a half to three days depending on the size, with your supply off for part of it.
That makes it workable where solar is not: a shaded or north-facing roof, a conservation area, or a listed building subject to consent, which the installer checks at survey, or a house whose owner would simply rather not have panels on it. If solar does suit you, we will say so — panels and a battery work well together.
| Cost | Today | With tariff and battery | Difference |
|---|---|---|---|
| Daytime units | £4,023 15,286 kWh at 26.32p | £59 211 kWh at 28p | −£3,964 |
| Overnight units | £0 | £1,294 16,170 kWh at 8p | +£1,294 |
| Standing charge | £200 | £200 | £0 |
| Annual total | £4,223 | £1,553 | −£2,670 |
| Shown after 10% caution | −£2,403 | ||
| Ten years, after paying for the battery | £11,530 ahead |
We work out whether a battery pays for your house and, if it does, introduce you to an installer. We do not install anything. The installer pays us a percentage of the installed price when the work is finished. You pay the installer directly and never pay us.
What happens next
How we would work it out for you
Answer four questions
You get a saving, a price and a payback before we ask for anything.
Send a year of bills and three photographs
Your meter, your fuse board and where the battery would go.
We model the tariffs
We run your usage against the time-of-use tariffs available at your postcode, with storage and without it.
You get a sized system, a payback, and what we earn
Battery capacity, inverter size, installed cost and the saving we expect, with the assumptions written down beside them.
Questions people ask first
Do I need solar panels first?
No. A battery on a time-of-use tariff saves money on its own by buying overnight and using it at peak. If you already have solar, tell us on the estimate — it changes the numbers rather than the answer. This first estimate assumes no panels, so your real saving from the battery will be lower.
What if I do not have a smart meter?
You will need one. Time-of-use tariffs depend on half-hourly readings, and suppliers fit smart meters at no charge. If you would rather not have one, this is not the right product for you and we will say so early. If your supplier has tried and could not get a signal, tell us — Economy 7 may still be open to you, on a narrower saving.
How are you paid, and does it change your advice?
We work out whether a battery pays for your house and, if it does, introduce you to an installer. We do not install anything. The installer pays us a percentage of the installed price when the work is finished. You pay the installer directly and never pay us. A bigger job could in principle be worth more to whoever pays that fee, so we don't ask you to take our word for it: every recommendation shows the payback arithmetic, and we'll tell you plainly when the numbers don't add up, including when the honest answer is not to buy at all.
What happens if tariff prices change?
Your saving changes with them. That is why every figure we give you is dated and carries its assumptions.
Will it keep the house running in a power cut?
Only if it is wired for backup, which is priced as its own line. A full 20 kWh battery runs about 400 W of essentials — lights, fridge, freezer, router — for about 45 hours. What stays on, what waits, and what it adds to the price.
What would your own house save?
Four questions. No contact details until there is a figure to send you, and the workings beside it when there is. If a battery is not worth it for your house, that is a real answer too.