The one number that matters most: SCOP
A heat pump moves heat rather than making it, so it can deliver several units of heat for each unit of electricity. The ratio at one moment is the COP; averaged over a whole heating season it's the SCOP (seasonal coefficient of performance), also called SPF. It depends on your climate, how warm your radiators or floor need to run, and how well the system is designed and installed. That's why we show a sensitivity chart: the difference between a SCOP of 2.5 and 4 is often bigger than the difference between two electricity tariffs.
How the comparison works
Starting from your current gas use is usually the most reliable estimate of heat demand you have: it reflects your actual house, thermostat setting and climate. Gas used for cooking is small and is counted as heating here. If you have an energy certificate or a heat-loss survey, switch to the “I know my heat demand” option.
The break-even SCOP tells you how efficient the heat pump must be just to match your boiler's energy cost. If your installer's design SCOP is comfortably above it, the heat pump should be cheaper to run. Dropping the gas standing charge by disconnecting completely can tip the balance further.
Gas units, explained
Gas is billed in different units in different places. We convert everything to kWh: 1 therm = 100,000 Btu = 29.31 kWh (US); 1 MJ = 0.2778 kWh and 1 GJ = 277.8 kWh (Australia and parts of Canada); and for cubic metres we use 10.72 kWh/m³, derived from EIA's average heat content of 1,036 Btu per cubic foot — your bill may list your utility's own figure, which you can enter.
Reference prices used as defaults
| Default | Country | Value | Source and period |
|---|---|---|---|
| Electricity | US | 18.31¢/kWh | U.S. EIA, Electric Power Monthly, Table 5.6.A, July 2026 (preliminary) |
| Electricity | UK | 26.32p/kWh | Ofgem, 1 Oct – 31 Dec 2026 |
| Electricity | Canada | — | No verified national figure on file — the field asks for your own rate. |
| Electricity | Australia | — | No verified national figure on file — the field asks for your own rate. |
| Gas (country's usual unit) | US | $1.481/therm | U.S. EIA, Natural Gas Prices (annual), 2025 (annual average) |
| Gas (country's usual unit) | UK | 7.97p/kWh | Ofgem, 1 Oct – 31 Dec 2026 |
| Gas (country's usual unit) | Canada | — | No verified national figure on file — the field asks for your own rate. |
| Gas (country's usual unit) | Australia | — | No verified national figure on file — the field asks for your own rate. |
| Gas standing charge | US | — | No verified national figure on file — the field asks for your own rate. |
| Gas standing charge | UK | 29.68p/day | Ofgem, 1 Oct – 31 Dec 2026 |
| Gas standing charge | Canada | — | No verified national figure on file — the field asks for your own rate. |
| Gas standing charge | Australia | — | No verified national figure on file — the field asks for your own rate. |
The U.S. gas default is EIA's 2025 annual average residential price ($15.34 per thousand cubic feet, about $1.48 per therm). Monthly residential gas prices swing a lot with the seasons because fixed charges are spread over very different volumes, so an annual average is a better guide for a heating estimate than a single month.
What's not included
This is a running-cost comparison. It leaves out installation costs, grants and rebates, servicing, and any changes to your hot-water setup. Comparing fuels other than gas? The Home Heating Cost calculator covers heating oil, propane/LPG and electric heaters too.
Sources
- U.S. Department of Energy — Heat pump systems
- Ofgem — Energy price cap unit rates and standing charges
- U.S. EIA — Natural gas prices (annual residential average)
- U.S. EIA — British thermal units (heat content of fuels)
- Natural Resources Canada — Heat pump basics
Results are estimates based on the figures you enter and the stated assumptions. They are not financial, tax, legal or engineering advice. Spotted a problem? Tell us.