Boiler Running Cost Calculator
Estimate how much your boiler costs to run per hour, day, month and year. Enter your boiler's output, efficiency rating, how many hours it runs, and your current gas unit rate.
Calculator
Found on your boiler's dataplate. Typical: 24–35 kW.
A-rated ErP = 90%+. Pre-2005 boilers often 60–70%.
Average UK home: 8–10 h/day in winter.
Ofgem price cap (Apr 2025): ~7.0 p/kWh. Check your bill.
Estimated running costs
How the calculation works
A boiler's output rating is the amount of useful heat it delivers. But because no boiler is 100% efficient, it actually burns more gas than the heat it delivers. The input power (gas consumed) is:
The cost per hour is then simply the input power multiplied by the gas unit rate (converted from pence to pounds):
Daily cost multiplies the hourly rate by hours run. Monthly cost uses 30.44 days (average calendar month). Yearly cost uses 365 days.
Tips to reduce your boiler running costs
- • Upgrade to a modern condensing boiler. Modern A-rated boilers run at 90–94% efficiency, compared to 60–70% for pre-2005 models. Replacing an old boiler can cut heating bills by up to 30%.
- • Use a programmable thermostat or smart thermostat. Reducing your heating by just 1 °C can save around £80–£100 per year.
- • Service your boiler annually. A well-maintained boiler runs more efficiently and is less likely to break down mid-winter.
- • Insulate your home. Loft and cavity wall insulation reduces heat loss, so your boiler doesn't need to work as hard or run as long.
- • Bleed your radiators. Trapped air stops radiators heating evenly, forcing the boiler to run longer cycles.
- • Lower the boiler flow temperature. Setting the flow temperature to 60 °C instead of 75 °C on a combi boiler can improve efficiency by 6–8%, particularly for condensing boilers.