Savings
Bill saving at your tariff
- where
- annual bill saving (£)
- annual fuel saved (kWh)
- unit rate (p/kWh)
Explain this equation
Converts the fuel saved each year into pounds on the bill.
Fuel saved in kWh times the unit rate in pence gives pence; dividing by 100 gives pounds.
Cost equals energy times price.
Sense check: 5,760 kWh of gas at about 8p is about £460 a year.
Watch out: standing charges do not change, and tariffs move, so present this as an estimate at today's rates.
Converts a fuel saving in kWh into pounds per year at the customer’s unit rate.
Enter your values to see the result.
Good to know
Default 7.97p/kWh is Ofgem’s average gas unit rate for 1 October–31 December 2026 (Direct Debit, including VAT); electricity is 26.32p/kWh. Use the rate on the customer’s bill where you have it. Standing charges do not change with insulation, so leave them out.
Common mistake
Using the electricity rate for a gas-heated home, or the reverse.
Limits
The price cap changes every quarter. Savings at a fixed price; future prices are unknown.
Sources
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow BS EN ISO 6946, BS 5250, PAS 2035, Building Regulations Part L and manufacturers’ data. Whole-house retrofit needs a qualified retrofit assessor and coordinator.