Solar Battery Storage: Costs, Size and Payback
Solar batteries, made simple
Do you need a solar battery?
A battery saves spare solar power so you can use it later. It does not make more power. It may help if your panels make power in the day but your home uses more in the evening.
How much does a battery cost?
Energy Saving Trust gives a wide range of £1,500 to £10,000. It gives about £4,600 as an example for a typical 5 kWh battery. The price depends on its size, power and how it is fitted.
What does 5 kWh mean?
kWh is the unit used on your electricity bill. A 5 kWh battery cannot always give you the full 5 kWh. Some power is kept back to protect the battery. Ask for its usable capacity. That is the amount you can normally use.
Choose a size from your real use
Look at how much solar power you send to the grid on a sunny day. Then look at how much power you use after the sun goes down. These two numbers give a better guide than the size of your house.
Too large
The battery may stay partly empty, mainly in winter.
Too small
It may fill early, so more spare power goes to the grid.
About right
It stores a useful share of your spare power for later.
A battery loses some power
Some energy is lost when the battery charges and gives power back. Using solar power at once is usually more efficient than storing it first.
Backup during a power cut is not automatic
Many batteries switch off when the grid goes down. If backup matters to you, ask which lights or sockets will keep working and for how long.
If backup matters, get five answers in writing
- Which lights, sockets or appliances will stay on?
- What is the highest power the backup can give at one time?
- How much battery capacity is kept back for a power cut?
- Can the solar panels recharge the battery while the grid is down?
- Does backup start by itself, and how will you test it safely?
Remember: energy kept for an emergency is not available for normal evening use. Ask the installer to show the backup working and leave simple instructions in your handover pack.
Questions to ask
- What is the usable size in kWh?
- How much power can it give at one time?
- How much energy is lost?
- How long is the warranty?
- Will it work in a power cut?
- Is the app free to use?
- What is the full installed price?
Existing system fault? If the battery, inverter or monitoring has stopped working, start with the solar PV fault and repair checker before booking a call-out.
Sources and official guidance3
Optional next step
Trying to decide if a battery is worth it?
Ask for a quote that separates panel costs from battery costs so the payback is easier to judge.
- No pressure from Here4Solar
- Personalised home quote
- Check if solar could work
Compare at least three written quotes before choosing an installer.