How Much Can a Home Battery Save on a Cheap Night Tariff?
A home battery charged overnight on a cheap tariff can save a typical household roughly £400 to £570 a year, depending on how often it is fully used. Here is how the sums work, which tariffs to look at, and when a battery is worth it.
How a night tariff and a battery work together
Time-of-use tariffs charge much less for electricity at night. Some overnight rates are around 7p to 9p per kWh, compared with 26.32p per kWh on the standard price cap. A battery fills up during the cheap window and powers your home through the day and evening, so you buy far less at the full rate.
A worked example with a 10 kWh battery
- A 10 kWh battery gives you about 9 kWh of usable storage.
- Filling it overnight takes about 10 kWh, allowing for small losses. At 8p per kWh that costs about 80p.
- Using those 9 kWh during the day instead of buying at 26.32p saves about £2.37.
- That is about £1.57 a day. Used fully every day, that is around £570 a year. Used fully on 250 days, it is nearer £390 a year.
Across the UK, an 8 to 10 kWh battery typically costs £5,500 to £7,000 installed (see our cost guide). Fitted alongside new solar panels by us, a 10 kWh battery adds about £2,700, so tariff savings alone pay it back in roughly 5 to 7 years. The case is even stronger when the battery also stores your own solar.
Why a battery works best with solar
In winter, the battery mostly charges cheaply overnight. In spring and summer, your panels fill it for free during the day, and you use that solar in the evening instead of exporting it for around 12p and buying it back at 26p. Over a year, solar and battery together typically let you use most of your own generation, which is where the biggest savings are. See is solar worth it in Northamptonshire for the solar side of the sums.
Which tariffs to look at
- Octopus Flux: designed for homes with solar and a battery. It has a cheap window from 2am to 5am and pays more for exports between 4pm and 7pm. You need an MCS certificate for the installation.
- Octopus Go and Intelligent Octopus Go: very cheap overnight rates, but aimed mainly at electric car owners, so check eligibility if you only have a battery.
- Other suppliers' smart tariffs: several suppliers offer overnight or time-of-use tariffs. They all need a smart meter, and peak-time rates on some can be higher than the price cap, so check the full rate table.
When a battery is worth it
- You have solar panels already, or are fitting them at the same time.
- You use a lot of electricity in the evening.
- You are happy to switch to a smart or time-of-use tariff.
- You want some backup power during a power cut, which many hybrid systems can provide.
No garage? A battery can still go in a utility room, under the stairs or in a weatherproof outdoor unit. See where a home battery can go without a garage. Batteries fitted to homes are currently 0% VAT until 31 March 2027.