Explore the cost of storing surplus solar energy or charging from a cheaper electricity tariff. Understand losses, potential savings and whether payback is realistic.
These are what-if estimates, not a property-specific battery recommendation. Your installer should assess load profiles, tariffs and export terms.
✓ Results update as you change the values.
Illustrative constant annual savings over the selected battery life. Crossing the cost line indicates simple payback; this is not a full lifetime forecast.
Cumulative savings Net upfront cost
Choose your battery and tariff assumptions.
Use a competent installer to assess battery location, fire protection, ventilation, escape routes, electrical safety and applicable UK requirements, including PAS 63100:2024 and BS 7671. Never obstruct escape routes or assume indoor installation is suitable. Confirm any grid connection or export permissions. Most batteries do not automatically provide power during an outage.
Solar mode deducts the export income that would have been received without the battery. Tariff mode deducts the electricity bought at the cheaper charging rate. Battery losses are included, and the calculator models only one use case at a time.
Hourly usage, sunny versus cloudy days, charge/discharge restrictions, export agreements, battery degradation, tariff changes, installation costs, and replacement after warranty can significantly alter actual benefits. The results are a planning scenario only.
Solar mode: daily battery output = min(usable capacity, later consumption, spare solar generation × round-trip efficiency). Solar diverted from export = battery output ÷ efficiency. Daily financial benefit = output × import tariff − diverted solar × export tariff. Annual values are daily estimates × chosen active days; this is not a PVGIS or hourly self-consumption simulation.
Off-peak mode: output = min(usable capacity, later demand); required off-peak charging electricity = output ÷ round-trip efficiency. Daily benefit = output × peak tariff − purchased charging electricity × off-peak tariff. No household electricity is generated by the battery.
Simple payback divides net upfront cost by positive annual net benefit. A negative or zero net benefit means no positive payback. A payback longer than chosen battery planning life is identified clearly. Chart totals assume constant yearly benefit, ignoring capacity degradation, maintenance, financing, inflation, warranty limitations, inverter replacement, safety constraints and tariff or seasonal changes. No carbon estimate is provided because time-dependent grid emissions, charge source and round-trip loss require an assessed model.
Reference source: Energy Saving Trust battery storage guide, accessed 2 November 2026; indicative 5kWh installed system around £4,600, typical life around 10–12 years. The initial 90% round-trip efficiency, 250 active days, demand, solar surplus and tariffs are editable hypothetical examples, not verified UK or property averages. Obtain several itemised installer quotes and verify export/time-of-use tariff conditions before buying.