Solar battery payback calculator
How to calculate whether a UK solar battery improves payback, using avoided imports, displaced export income, supported battery flows and battery cost.
Key takeaways
- Run the solar-only case first, then add the battery as a separate extra.
- The battery earns value by shifting exported solar into later self-use, but it may reduce export income.
- A battery can still be worthwhile for resilience or tariff flexibility, even when pure payback is long.
Use the extra-benefit method
A solar battery payback calculator should answer one question: how much extra annual benefit does the battery create compared with no battery?
The clean formula is battery payback = battery cost divided by extra annual benefit. Extra annual benefit means the additional bill saving after allowing for any export income you no longer receive.
Why blended payback can mislead
If you combine solar and battery into one total cost, the solar panels can make the whole package look healthier than the battery itself. That doesn't mean the battery is bad. It means you need to judge the extra decision separately.
For example, a solar-only system might pay back in a reasonable time. Add a battery, and annual benefit may rise only modestly while the upfront cost rises by several thousand pounds.
What changes the battery result
The battery looks better when evening electricity use is high, import rates are much higher than export rates, and the battery is used regularly. It looks worse when the household already uses plenty of electricity during the day or has a strong export tariff.
Time-of-use tariffs can improve the case, but they add rules. Some households charge the battery from cheap overnight electricity and use it later. Some tariffs have export conditions. Read the terms before assuming the battery can arbitrage every price gap.
What to enter in the calculator
Complete the solar-only estimate first using your quote, generation, household electricity use and tariffs. Then opt into battery comparison, enter the usable battery capacity and incremental installed battery cost, and choose Compare battery.
The current calculator does not ask you to choose a self-consumption uplift. For supported combinations it estimates annual solar energy sent into the battery and energy later delivered to the home, then values avoided import and displaced export separately. It does not model grid charging or time-of-use arbitrage.
- Battery capacity: use the usable capacity from the quote.
- Battery cost: use the incremental installed cost of adding storage, not a hardware-only price or blended total.
- Export rate: keep it realistic because charging the battery can displace export income.
- Warranty, cycle life and backup capability: check these separately because they are not modelled by the calculator.
Sources checked
- Energy Saving Trust battery storage guideConsumer guidance on home battery costs, storage limits and tariff use.
- Ofgem SEG supplier listCurrent SEG licensee list and annual supplier status.
- Ofgem energy price cap unit ratesCurrent unit-rate context for electricity tariffs.