Home Batteries Explained: Do You Need One With Solar Panels?

A home battery stores electricity so that you can use it later, rather than sending it to the grid or buying it when prices are high. Batteries are often sold alongside solar panels, but they can also work with time-of-use tariffs without solar. They are a significant purchase, so it pays to understand how they earn their keep.

How a home battery works

A battery can charge from your solar panels, from the grid at cheap times, or both. It then releases the stored energy when you need it, typically in the evening when solar panels are not producing and prices may be higher. A control system decides when to charge and discharge.

Key terms

Capacity (kWh): how much energy the battery can store. A typical home battery is a few kWh up to around 10 kWh or more.
Usable capacity: the portion you can actually use. Batteries are not discharged completely, so check this figure rather than the headline.
Power output (kW): how much the battery can supply at once. A low power rating may not run several appliances together.
Round-trip efficiency: the percentage of energy you get back out compared with what you put in. Some energy is always lost.
Cycles and warranty: how many charge and discharge cycles it is designed for and the guaranteed lifespan.

When a battery makes sense

You have solar panels and use most of your electricity in the evening, so you waste a lot of generation at midday.
Your export payment is low compared with the price you pay for imported electricity.
You are on a time-of-use tariff with a big gap between cheap and expensive rates. See Economy 7 and time-of-use tariffs.
You want some backup during power cuts, which requires a system designed for it and not all batteries provide.

When it may not

If you are out all day and use little electricity, a battery may take a long time to repay its cost. The financial case depends on the price difference between buying and selling, and on the cost of the battery, so do the sums with your own figures. Some batteries may not pay back before they need replacing, so ask installers for a realistic payback estimate with assumptions you can check.

Safety and installation

Choose a battery installed by a qualified, certified installer, as it involves high-voltage electrical work. Consider where it will be placed: garages and utility rooms are common, and manufacturers and regulations set requirements for ventilation and fire safety. Tell your insurer and your network operator.

Retrofit or at the same time as solar?

Installing a battery at the same time as solar panels may reduce labour costs and ensure the system is designed as a whole. Adding a battery later is possible but depends on whether your inverter is compatible, and whether the battery is AC-coupled or DC-coupled. Ask your installer to explain the difference.

VAT and support

HMRC guidance shows that installing batteries is zero-rated for VAT in the UK until 31 March 2027. Check what applies when you buy. See also our solar panel guide.

A battery can be a useful addition, but it is not a necessity. Compare quotes carefully and consider smaller, cheaper options if your evening use is modest.