Solar battery storage: is it worth adding?

What a battery does

Solar panels produce most in the middle of the day, when many homes use least. Without a battery, the spare power is exported to the grid for a few pence per unit. A battery stores it so you can use it in the evening instead of buying electricity.

How much more of your own power you use

MCS lookup tables show how much a battery of 4 to 5kWh usable capacity raises the share of solar power a home uses itself. For a home using 2,500 to 2,999kWh a year (Ofgem’s typical home uses 2,500kWh) with a system making about 3,600 to 3,900kWh:

• 23% to 54% if someone is home all day
• 19% to 52% if you are home half the day
• 14% to 48% if you are out all day

Some energy is lost in storing it, so using power straight from the panels is always the most efficient.

What it costs

The Energy Saving Trust says a typical home battery might be 10kWh, with costs ranging from £1,500 to £10,000. A 5kWh battery costs about £4,600. Which? found some energy suppliers’ battery packages start from around £2,500 (Ovo) and about £4,000 (EDF).

VAT on batteries

Since 1 February 2024, batteries installed in homes are zero-rated for VAT, whether fitted with new panels, added to existing panels later, or installed on their own. This is due to end on 31 March 2027, when the rate rises to 5%.

Using cheap overnight electricity

Some tariffs let a battery work harder. For example, Octopus Flux has a cheap period from 2am to 5am for charging the battery and a higher rate from 4pm to 7pm for using or exporting it. You need solar, a battery and a smart meter, and you are usually expected to manage the battery’s timings yourself. Check the current terms with the supplier.

How long batteries last

Expect around 10 to 12 years, with most sold with a 10-year warranty. Panels last 25 years or more, so you should plan to replace the battery at least once.

So is it worth it?

A battery makes most sense if you are out during the day and use most of your electricity in the evening, or if you can use a time-of-use tariff. If you are home all day, panels alone already cover a good share of your use.

Fitting the battery at the same time as the panels is usually cheaper than adding it later, because the installation is done in one visit.

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