Heating Cost Comparison Calculator

Comparing heating systems means comparing three things at once: how much heat the building needs, how efficiently each system produces it, and what each fuel costs. Change any one and the answer changes, which is why blanket claims about one technology being cheaper are usually wrong somewhere.

Efficiency here is expressed as a factor. A condensing gas boiler is around 0.88; a heat pump has a seasonal coefficient of performance typically between 2.5 and 4, meaning it delivers several units of heat per unit of electricity.

The calculation

Fuel used = heat needed ÷ efficiency factor. Annual cost = fuel used × price per kWh. The payback on switching is the extra installation cost divided by the annual running saving.

Worked example

A house needing 15,000 kWh of heat. A gas boiler at 0.88 efficiency burns 17,045 kWh at 0.07, costing 1,193 a year. A heat pump with a seasonal factor of 3.2 uses 4,688 kWh of electricity at 0.28, costing 1,313. At these prices the heat pump costs 120 a year more to run, so the 8,000 installation premium never repays on running cost alone.

The price ratio is what decides it

A heat pump beats a gas boiler when the electricity-to-gas price ratio is below roughly the coefficient of performance divided by boiler efficiency — about 3.6 in the example above. At a ratio of 4.0, as used here, gas wins. This is why the same technology is clearly cheaper in one country and clearly not in another.

Frequently asked questions