Home battery savings calculator
What a home battery would really have saved on Octopus Agile in North Scotland, from every half-hour price between Wednesday 23 September and Thursday 22 October.
The short answer
With Octopus Agile prices in North Scotland over the last 30 days, a 10 kWh home battery (5 kW) charging overnight and running a home that uses 2,700 kWh a year would have saved about £34.69, or £422 a year at that rate. At £5,000 installed, that pays back in about 12 years.
Your battery and your home
- Saved in 30 days
- £34.69
- Per year, at this rate
- £422
- Payback
- 12 years
- Bill cut
- 43%
Compared with the same home on Agile without a battery. Best case: the battery knows each day's prices, charges from the grid and powers the house, never exporting, with 90% round-trip efficiency. Use follows a typical home's daily pattern. Prices from Octopus Energy's public API (AGILE-24-10-01), including VAT. Not affiliated with Octopus Energy.
What makes the biggest difference
- Evening use. The battery only saves money on power the home would have bought at peak prices. A battery much bigger than your evening use mostly sits idle.
- The price gap. Windy months with cheap nights save the most. Calm months with flat prices save little. Change region above to compare.
- Solar panels. Not included here. Storing your own daytime solar for the evening usually adds more than grid charging alone.
- Exporting. Selling stored power back at the peak on an export tariff can add more, but is not counted here.
Planning when to charge? See today's cheapest times and the 7-day forecast.
Common questions
How much can a home battery save on Octopus Agile?
It depends on how much electricity you use in the evening and how big the gap is between night and peak prices. A typical home using 2,700 kWh a year with a 10 kWh battery often saves a few hundred pounds a year by filling the battery overnight and running the house from it in the 4pm to 7pm peak. The calculator works it out from the last 30 days of real Agile prices in your region.
How long does a home battery take to pay for itself?
Divide what the battery cost to install by what it saves in a year. On Agile alone, without solar panels or exporting, payback is often 10 years or more, which is close to a battery's working life, so check the numbers for your own use before buying. Solar panels and an export tariff shorten it.
Does the calculator include exporting to the grid?
No. It only counts the electricity your home would otherwise have bought, which is the safest estimate. Exporting at peak times on a tariff like Agile Outgoing can add to the savings, but needs an export meter and approval from your network operator.
How accurate is this?
It is the best case: it assumes the battery knows every price in advance, which is close to what smart battery apps manage once prices are published at 4pm. It uses a typical home's daily pattern of use, scaled to the yearly total you enter, and 90% round-trip efficiency. Real savings are usually a little lower.