In short: a battery lets you use more of your own solar power in the evening instead of exporting it cheaply. It usually makes most sense if you are out during the day, or if you can also charge it on a cheap overnight tariff.
What a battery does
Solar panels produce most in the middle of the day, when many homes use the least. Without a battery, a typical home uses roughly half of what its panels make and exports the rest. A battery stores that spare power so you can use it in the evening, when electricity from the grid costs most.
When a battery is worth it
- You are out at work during the day and use most of your electricity in the evening.
- Your export tariff pays much less than you pay for electricity.
- You are on, or can switch to, a time-of-use tariff with cheap overnight rates. The battery can charge at night in winter, when the panels produce little.
- You are installing panels anyway, so you only pay for the installation once.
When it may not be
- Someone is home all day and already uses most of the solar power.
- You have a small system with little spare power to store.
- You get a high export rate, so selling the spare power earns nearly as much as using it.
What size do I need?
Most home batteries hold between 5 and 10 kWh. A good starting point is to match the battery to your evening and overnight use. Bigger is not always better, because a battery that never fills up is money spent for nothing.
Adding a battery later
You can add a battery to existing panels. A “hybrid” inverter makes this simpler, so it is worth asking for one when you first install. Batteries for existing systems are covered by the same 0% VAT rate until 31 March 2027.
Thinking about panels and a battery?
Installers can size a battery to how you actually use electricity.