One of the biggest questions UK homeowners have is whether a heat pump will be cheaper to run than their current boiler. The honest answer: usually yes if it's well-designed and you're on the right tariff — but not automatically.
SCOP — the number that matters
Seasonal Coefficient of Performance (SCOP) is the heat pump's annual efficiency. A SCOP of 3.5 means 3.5 kWh of heat for every 1 kWh of electricity used. Most modern air source heat pumps target SCOP 3.0–4.5 depending on system design and house.
Heat pump vs gas boiler running costs
For a typical UK home needing about 12,000 kWh of heat a year, using unit rates of roughly 6p/kWh for gas and 25p/kWh for standard electricity:
| Heating system | Efficiency | Electricity / gas rate | Illustrative annual cost |
|---|---|---|---|
| Gas boiler | ~85% | 6p/kWh gas | ~£850 |
| Oil boiler | ~85% | ~8p/kWh oil | ~£1,130 |
| Heat pump, standard tariff | SCOP 3.5 | 25p/kWh electricity | ~£860 |
| Heat pump, heat-pump tariff | SCOP 3.5 | ~15p/kWh blended | ~£515 |
| Heat pump, poorly designed | SCOP 2.5 | 25p/kWh electricity | ~£1,200 |
These figures are illustrative arithmetic from the rates and efficiencies shown, not survey results. The pattern matters more than the numbers: a well-designed heat pump on the right tariff usually beats gas, a badly designed one on a standard tariff does not. Ask every installer to state the SCOP their design achieves and which tariff their running-cost estimate assumes.
How to maximise savings
- Choose an experienced MCS-certified installer who designs to a low flow temperature
- Switch to a heat-pump-friendly time-of-use tariff
- Insulate before installing where possible
- Pair with solar and a battery to offset peak-rate use
Get heat pump quotes that include estimated annual running cost on your tariff.