A home battery is often the biggest decision after choosing solar panels. It adds a few thousand pounds to the cost, so it's fair to ask whether it pays its way. For most households with solar, the answer is yes, but how much it's worth depends on when you use electricity and which tariff you're on.
What a battery actually does
Solar panels generate most during the middle of the day. Most homes use the most electricity in the morning and evening. Without a battery, the solar you don't use straight away is exported to the grid, usually for much less than you pay to buy electricity back later.
A battery stores that spare daytime solar so you can use it in the evening instead of buying from the grid. Without a battery, a typical home uses roughly 30 to 50% of its solar. With a battery, that can rise to around 70 to 80%.
The overnight tariff effect
A battery can also charge from the grid overnight when electricity is cheap, then power your home at peak times. Several suppliers offer smart or overnight tariffs with off-peak rates well below the standard price, so every unit you shift from peak to off-peak saves money.
This matters most in winter, when your panels generate less. In summer the battery fills with free solar; in winter it fills with cheap overnight power. That means the battery keeps saving you money all year round, not just in the sunny months.
Who saves the most
- Households that are out at work or school during the day
- Homes with higher evening use: cooking, washing, family routines
- Anyone willing to switch to a smart or overnight tariff
- Homes with an electric car or heat pump, which use a lot of electricity
What size battery do you need?
Most homes suit a battery of around 5 to 10kWh. A good rule of thumb is to match the battery to your typical evening and overnight use. Bigger isn't always better: a battery that never fills up, or never empties, isn't earning its keep. Your installer will look at your usage and recommend a size.
Can I add a battery later?
Yes. If you're not ready for a battery now, ask for a hybrid inverter with your solar panels. That makes it much simpler to add a battery later without replacing your system. Batteries can also be added to most existing solar systems.