Free Tool

Battery Storage Savings Calculator

See what a home battery could save you, which size suits your home and how long it takes to pay back, with or without solar panels.

Last updated: 23 October 2026 · Electricity 26.32p/kWh · Export 4p to 15p/kWh · Overnight 9.4p/kWh

Your home
Do you have solar panels?
Solar system size It's on your quote or MCS certificate, in kWp.
What are you paid for exported electricity? Every kWh the battery stores is a kWh you no longer export, so a high export rate makes a battery worth less.
Annual electricity bill: £1,200 What you pay for electricity in a year, including the standing charge.
£400£3,000
When is someone usually at home?
Are you on a cheap overnight tariff? For example Octopus Go, about 9.4p overnight and 33p to 36p the rest of the day, if you have an electric car you charge at home. Without one, Agile Octopus, or Cosy Octopus if you have electric heating, can also give you cheap overnight electricity.
Battery size We've picked the size that suits your answers. Try the others to compare.
Your estimate
Yearly saving
£0
from the battery
Self-sufficiency
0%
of your electricity from your own solar
Typical install cost
£0
Payback
0
at today's prices
Where the saving comes from
Storing your solar
£0
Cheap overnight charging
£0
Batteries at this size

The payback is only part of the story

A battery usually takes longer to pay for itself than solar panels. Many owners buy one for these reasons as well:

  • Using your own solar in the evening instead of selling it cheaply and buying it back at 26p or more.
  • Backup in a power cut. Some batteries can run the whole house, others only selected circuits, and some none at all without extra kit. Ask your installer which you're getting. If backup is the main reason, a portable power station gets you it for a fraction of the cost.
  • Extra income. Some suppliers pay you to use less at busy times, such as Octopus Saving Sessions. That isn't included in the figures.
  • Getting ready for an electric car or a heat pump, which both make cheap stored electricity more useful.

Which kind of quote suits you?

Your figures above are an estimate. An installer can check your usage, your inverter and where the battery can go, and give you a real price.

"I'd rather deal with one good installer" Get a quote from Blue Ape Renewables, the installer we work with. MCS-certified and NAPIT-accredited, fitting batteries and solar panels across England, Wales and Scotland. Get a quote →

Tell us about your project and local installers will quote

Both are free and there's no obligation. We earn a commission if you go ahead with Blue Ape or with one of the installers you are matched with.

Estimates only, not a quote. We take £200 a year off your bill for the standing charge and price the rest at 26.32p/kWh (Ofgem cap, October to December 2026), or at 34.4p if you choose a cheap overnight tariff, the middle of Octopus Go's 33.0p to 35.8p regional day rates, with 9.4p overnight. Octopus raised these rates on 20 October 2026, and Go's day rate is now above the standard price cap, so Go only pays if you can move a good share of your use overnight. Octopus Go needs an electric car you charge at home. Agile Octopus prices change every half hour, so your saving on it will differ. Export is valued at the rate you choose: 4p, 12p or 15p per kWh. We assume 950 kWh a year per kWp of solar, that 30% to 50% of it is used straight away depending on when you're home, and that the battery returns 90% of what it stores. Stored solar is limited by the size of the battery and by how much sunshine there is in winter, and overnight charging fills whatever space the solar leaves. How the sums work.

Rates last checked: 23 October 2026 · October price cap explained · Export tariffs compared

How the Battery Calculator Works

The calculator works out how much electricity a battery can move from a cheap time to an expensive one, and what that is worth to you.

1
Your bill becomes usage
We take £200 a year off for the standing charge and divide the rest by your unit rate. A £1,200 bill on a standard tariff is about 3,800 kWh a year.
2
Your panels make electricity
Each kWp of solar makes about 950 kWh a year in the UK. Without a battery you use 30% to 50% of it as it is made, depending on when you're home, and export the rest.
3
The battery stores what you would export
Every kWh stored and used later saves you the unit rate but loses the export payment, which is why the export rate you choose changes the result so much. In winter the panels rarely fill a battery, so we assume solar fills it to about 55% of its size on an average day.
4
Overnight charging fills the gap
On a tariff like Octopus Go the battery also charges at about 9.4p overnight and covers use at a day rate of about 34p. This is where most of the winter saving comes from. Go needs an electric car you charge at home. Without one, Agile Octopus prices are often lowest overnight, but they change every half hour.

Why GivEnergy Is No Longer in Our Picks

GivEnergy was one of the most popular battery brands in the UK. It entered administration on 9 April 2026, and its administrator has said it will not honour hardware warranties. If a quote offers a GivEnergy battery, ask the installer who would cover a fault, and compare it with a quote for another brand.

Frequently Asked Questions

Is a home battery worth it in the UK?

It depends mostly on your tariff. With solar on a standard tariff, a battery stores electricity you would have sold for your export rate and saves you 26.32p. At a 12p export rate the gain is about 12p per stored kWh after losses, and at 4p it is about 20p. Add a cheap overnight tariff and the battery works all year, which shortens the payback. Use the calculator above with your own bill to see where you land.

What size battery do I need?

Most homes with 3 to 4 kWp of solar suit a battery of about 10 kWh. Smaller homes and 2 kWp systems suit about 5 kWh. A 13.5 kWh battery usually only pays off if you use a lot of electricity in the evening or charge an electric car. The calculator marks the best fit for your answers.

Can I get a battery without solar panels?

Yes. On a time-of-use tariff, the battery charges cheaply overnight and powers your home during the day instead of buying at the day rate. Octopus Go is about 9.4p overnight but needs an electric car you charge at home. Without one, the usual choices are Agile Octopus, or Cosy Octopus if you have electric heating. On a standard flat-rate tariff it saves nothing, because there is no cheap electricity to store.

How much does a home battery cost to install?

Typical installed prices in our guide run from about £4,500 for a 5 kWh battery to £8,500 to £11,500 for a 13.5 kWh Tesla Powerwall 3. Batteries have 0% VAT until 31 March 2027. Adding one to an existing solar system can cost a little more because of the extra electrical work.

How long do home batteries last?

Most come with a 10-year warranty, usually with a promise to hold about 70% of their capacity by the end of it. That is why we compare the payback with 10 years: a battery that pays back well inside that is a good financial bet.

Will a battery keep my lights on in a power cut?

Not always. Some batteries can power the whole home with an extra gateway, some only selected circuits, and some switch off with the grid. If backup matters to you, ask the installer exactly what will work in a power cut before you sign. If you only need the essentials kept on, a portable power station costs from about £199 and needs no installation.

Last updated 23 October 2026. The calculator gives estimates, not quotes. Rates: Ofgem price cap for October to December 2026, Octopus Go rates from Octopus Energy's published tariff data on 23 October 2026, and export rates of 4p, 12p and 15p per kWh. Battery prices are typical installed ranges from our best home battery guide.