Heat pump running cost calculator — compare annual costs vs gas
Use this lookup table to sanity-check what an air-source heat pump might cost to run in a UK home. It compares home size, insulation level, expected seasonal efficiency and a realistic annual running-cost range against a typical gas boiler. It is a guide, not a substitute for a room-by-room heat-loss design.
Typical annual running costs by home type
| Home type | Insulation level | Heat demand | Expected SCOP | Heat pump | Gas boiler | Likely outcome |
|---|---|---|---|---|---|---|
| 2-bed flat / terrace | Good (EPC B–C) | 6,000–8,000 kWh | 3.4–3.8 | £390–£520/yr | £470–£620/yr | Heat pump often cheaper to run |
| 3-bed semi | Average (EPC C–D) | 10,000–13,000 kWh | 3.0–3.4 | £650–£950/yr | £780–£1,000/yr | Usually similar or slightly lower |
| 4-bed detached | Average (EPC D) | 14,000–18,000 kWh | 2.8–3.2 | £960–£1,420/yr | £1,090–£1,400/yr | Depends on tariff and flow temperature |
| Older detached / rural home | Poor (EPC E+) | 20,000–28,000 kWh | 2.4–2.9 | £1,520–£2,570/yr | £1,560–£2,180/yr | Can be higher until fabric upgrades are done |
| Renovated family home | Good + smart tariff | 11,000–15,000 kWh | 3.2–3.8 | £620–£1,030/yr | £860–£1,170/yr | Strong case for lower running costs |
Costs vary with weather, hot-water demand, thermostat settings, flow temperature and tariff choice. The table is designed to help you challenge vague sales claims — not to replace a proper heat-loss survey.
How to use this calculator sensibly
1. Start with the closest home type. The heat-demand band matters more than the number of bedrooms. A compact but draughty house can cost more to heat than a larger, renovated one.
2. Focus on SCOP, not headline COP. Sales literature often quotes a best-case test-point COP. Your annual running cost depends on the seasonal figure after winter weather, defrost cycles and hot-water production.
3. Treat insulation and emitter upgrades as part of the economics. Loft insulation, draught-proofing and a few larger radiators can reduce heat demand and improve efficiency at the same time.
4. Compare against the real alternative. If your current boiler is old or poorly maintained, your actual gas heating cost may already be worse than the average boiler range shown here.
Heat pump running cost FAQs
Are heat pumps always cheaper to run than gas boilers?
Not always. Running costs depend mainly on three things: your home's heat demand, the seasonal efficiency of the heat pump (SCOP), and the gap between your electricity and gas unit rates. In a well-insulated home with a correctly designed system and a sensible tariff, a heat pump is often competitive or cheaper. In a draughty home running at high flow temperatures, costs can be similar or sometimes higher until insulation and emitter upgrades are done.
What SCOP should I expect from an air-source heat pump in the UK?
A realistic SCOP for a good UK air-source heat pump installation is around 3.0 to 3.8 across the year. Smaller or well-insulated homes running low flow temperatures can be towards the top end. Older homes with higher-temperature radiators or poor fabric can land closer to 2.5 to 3.0. Treat any quote promising very high efficiency without explaining the design assumptions with caution.
Why does insulation matter so much to running costs?
Insulation cuts the total amount of heat your home needs. That matters for any heating system, but especially for heat pumps because lower heat demand often lets the system run at lower water temperatures, which improves efficiency. Loft insulation, cavity-wall insulation, draught-proofing and sensible radiator upgrades can make as much difference to running costs as the heat pump model itself.
Do smart tariffs reduce heat pump running costs?
They can. Some suppliers offer off-peak or heat-pump-friendly tariffs that lower the effective electricity rate for part of the day. That helps most in homes with good controls, weather compensation and enough thermal mass or hot-water flexibility to shift some demand. A specialist installer should explain whether your proposed system can make practical use of a smart tariff, rather than assuming maximum savings by default.
Can I estimate running costs from my current gas bill?
Yes, roughly. Your current annual gas use gives a useful clue to the home's heat demand once you allow for boiler efficiency. A rough comparison is: annual heat demand ÷ expected SCOP = heat pump electricity use. Multiply that by your electricity tariff to estimate annual running cost. A proper installer will refine this using a room-by-room heat-loss calculation, not just your old bills.
What should I ask an installer about running-cost estimates?
Ask what heat-loss figure they used, what flow temperature they designed around, what SCOP or SPF they expect, whether radiator upgrades are included, and what tariff assumptions sit behind the estimate. If the running-cost claim looks much better than competing quotes, the difference is usually in one of those assumptions.
Want a property-specific running-cost estimate?
A good installer will size the system from a room-by-room heat-loss calculation, explain the target flow temperature, and show how they arrived at the expected annual efficiency.