Battery Storage Payback Calculator UK 2026

Rates and data last verified 4 October 2026 by the ExpertSure editorial team. Sources are listed in the methodology below the calculator.

This battery storage payback calculator estimates annual electricity savings, simple payback and net returns over 10 and 15 years. With the default inputs of a 10 kWh battery, 6 kWh of surplus solar a day and electricity at 26.32p/kWh, it estimates about £467 in annual savings and 11.8 years to recover its assumed £5,500 cost. The electricity default is Ofgem’s average Direct Debit unit rate for 1 October to 31 December 2026, which carries no VAT until 31 March 2027; use the rate on your own bill. The result is an illustration based on fixed assumptions, not a forecast or installation quote.

How to Use This Calculator

Select your battery capacity — compare 5 kWh, 10 kWh and 13.5 kWh against the electricity you can store and use each day.

Indicate whether you have solar panels — the solar option deducts a fixed 5p/kWh export payment; the no-solar option assumes charging at a fixed 7.5p/kWh off-peak rate.

Enter your average daily solar export (use your export meter or monitoring app) and current electricity unit rate. A sunny summer day is not a year-round average.

Review your simple payback period, annual saving and 10- and 15-year net returns. Read the model assumptions below before comparing the result with a quote.

What the Calculator Assumes

The model uses fixed battery costs of £3,000 for 5 kWh, £5,500 for 10 kWh and £9,500 for 13.5 kWh. These are calculation assumptions, not current supplier prices. It treats 90% of the selected capacity as usable. With solar, the energy stored each day is the smaller of your daily surplus and that usable capacity. Each stored kWh saves your electricity rate minus an assumed 5p export payment. Without solar, the model assumes a full usable charge each day at 7.5p/kWh. Check whether your tariff and consumption allow that.

Annual savings equal daily savings multiplied by 365. Simple payback divides the assumed battery cost by annual savings. Net returns subtract that cost from 10 or 15 years of unchanged savings. The model does not separately account for charging and discharging losses, battery degradation, maintenance, replacement, financing or changing tariffs. Its 90% usable-capacity allowance is not a conversion-efficiency calculation. A result extending beyond your battery’s useful life would not represent a recovered investment.

Comparing a specific system? Read our Tesla Powerwall 3 cost guide for its installed-price breakdown and compare a written quote with the calculator’s fixed cost assumption.