A heat pump can cost less to run than a gas boiler, but the result depends on electricity and gas prices, seasonal performance and how much heat your home needs. Compare the cost of delivering the same useful heat, then add standing charges and maintenance. A lower energy bill does not automatically mean the installation will pay for itself.
How do you compare heat pump and boiler running costs?
A gas boiler converts fuel into heat; a heat pump uses electricity to move heat. Their purchased energy requirements therefore differ even when they deliver the same amount of warmth.
For a simplified energy comparison, divide each unit price by the relevant seasonal efficiency or performance factor:
- Gas boiler: gas price per kWh ÷ seasonal efficiency expressed as a decimal.
- Heat pump: electricity price per kWh ÷ seasonal performance factor, or SPF.
An assumed boiler efficiency of 90% becomes 0.90 in the calculation. A heat pump SPF of 3 means three units of heat output for each unit of electricity over the assessed period. These are calculation inputs, not promises about a particular installation.
Use the same boundary for both systems: space heating alone, or space heating plus hot water. Ask whether the heat-pump estimate includes circulation pumps, controls and backup electric heating; add any excluded consumption separately.
Worked example: the cost of delivering 10,000 kWh of heat
This illustration uses Ofgem's average Direct Debit price-cap unit rates for 1 October to 31 December 2026: electricity at 26.32p/kWh and gas at 7.97p/kWh. These averages cover England, Scotland and Wales, not Northern Ireland. Your tariff and regional rates may differ.
The selected heat demand is simply a comparison quantity. Holding these prices constant does not make the result an annual bill forecast.
Swipe across to read the table.
Figures are rounded. The table excludes standing charges, maintenance, installation and boiler auxiliary electricity. Heat-pump figures assume the chosen SPF covers all electricity required within the assessed system boundary.
At SPF 3, the difference is small enough that the omitted costs could change the overall result. Recalculate with your own rates before making a decision.
Ask for a property-specific seasonal estimate and its assumptions. A single coefficient of performance, or COP, describes particular operating conditions; it should not be treated as a full-year result.
Discuss the proposed flow temperature, radiator suitability, local weather assumptions and hot-water settings with the installer. Government heat-pump guidance identifies home efficiency and tariff choice as factors in running costs, and recommends discussing heat loss and possible radiator upgrades.
Request separate explanations of space-heating and hot-water demand, plus any immersion or backup heater use. Check whether the estimate measures heat at the appliance or includes distribution and storage losses.
Insulation improvements can reduce the heat either system must supply. For that separate decision, see our guide to improving your home's heating efficiency. Property age alone is not a running-cost calculation.
How do tariffs and standing charges change the answer?
For a time-of-use tariff, calculate the electricity price weighted by when the heat pump actually runs. Using only the cheapest overnight rate can understate costs if substantial heating happens at other times.
Include the effect of changing tariff on the household's other electricity use. Compare daily standing charges too: a cheaper heating unit rate does not necessarily produce the lowest whole-home bill.
Do not count the gas standing charge as a saving if you retain a gas supply for cooking or another appliance. Ask the supplier what ending that supply involves and whether any charges apply.
If bills have recently risen, first separate price changes from increased consumption. Our guide to unexpected increases in heating bills explores that problem.
Build a comparison for your own household
- Collect consumption: use a full year of bills where available, noting weather, occupancy and thermostat changes.
- Estimate useful heat: gas-meter kWh are fuel input, not heat output. Account for cooking and other gas uses.
- Test assumptions: compare several seasonal-performance and energy-price scenarios rather than one optimistic figure.
- Add recurring costs: standing charges, servicing and any separately estimated auxiliary electricity.
- Compare capital costs separately: installation, necessary system changes and confirmed financial support.
If you are deciding whether an existing boiler needs replacing at all, our boiler repair versus replacement guide addresses that earlier decision.
Ask for the calculations behind any savings estimate in writing. The useful comparison is a realistic range for your home, with the assumptions visible.