Battery vs No Battery

Without a battery, surplus solar energy is exported to the grid and you receive the Smart Export Guarantee (SEG) rate — typically 4–15p per kWh. With a battery, you store that energy and use it yourself instead of buying grid electricity at 25–30p per kWh. The financial case depends on how much surplus you generate and when you consume electricity.

The numbers

Assuming grid electricity at 28p/kWh and an SEG export rate of 8p/kWh, the difference in value between self-consuming a unit versus exporting it is 20p. A 10 kWh battery fully discharged every day saves roughly £730 per year at current rates — more if you are on a smart tariff that lets you charge cheaply overnight.

What a battery adds to the upfront cost

A quality 10 kWh battery adds £3,500–£5,500 to the cost of a solar installation. That extends the payback period from around 6–7 years to 9–11 years on the battery's portion of the investment. Lifetime returns improve substantially — from around £19,000 over 25 years to £30,000+.

When a battery makes the most sense

• You consume most of your electricity in the evening and overnight
• You are on or plan to switch to a smart tariff with off-peak rates
• You have an EV and want to charge it on cheap overnight grid electricity or stored solar
• You want greater energy resilience during grid outages, if the battery has backup capability

When a battery is probably not worth it

If you are home during the day and directly self-consume most of your generation, your surplus is small and a battery has less to do. If your panels are undersized relative to consumption, optimising the array should come before adding storage. We are direct about this at survey — we would rather you make the right decision than the more expensive one.