Home battery calculator (without solar)
See whether charging a battery at a cheaper rate and using the electricity later could lower your bill.
Typical: 2,700 kWh a year (Ofgem typical use)
Answer the first question to see your estimate.
Change assumptions
Defaults are planning assumptions. A quote or your bill should replace them.
How this estimate works
We split a typical day into half-hours, using a simple shape with low use overnight and peaks in the morning and evening. Use rises in winter and falls in summer.
Each day the battery charges only in the cheap period and is used only outside it. It can deliver the smallest of: its usable capacity; what its power can put in during the cheap period; and your use outside the cheap period, each half-hour limited by its power.
Storage losses are counted once: to deliver 1 kWh at 90% efficiency, the battery buys about 1.11 kWh at the cheap rate. If that costs more than the standard rate, we assume the battery is left idle, as a sensibly set-up battery would be.
Standing charges are included, so a tariff with a higher standing charge shows up in the “changing tariff” line, not as a battery saving. Real savings depend on the battery’s controls, standby use, ageing and how your use varies day to day.
Sources: Ofgem typical domestic consumption values; Energy Saving Trust: battery storage.
Have solar panels or planning them? Use the solar battery calculator. New to home batteries? Read the guide.