SCOP: the number that decides your bill
SCOP tells you how many units of heat a heat pump delivers for each unit of electricity, averaged over a year.
A SCOP of 3.5 means 1 kWh of electricity becomes 3.5 kWh of heat. A gas boiler turns 1 kWh of gas into about 0.85 kWh of heat. That efficiency gap is how a heat pump can be cheaper to run even though electricity costs more than gas.
What each SCOP costs
For a typical 3-bed semi-detached house at today’s prices:
| SCOP | Electricity used | Standard tariff | Cosy Octopus |
|---|---|---|---|
| 2.5 | 3,910 kWh | £1,029 | £766 |
| 2.8 | 3,491 kWh | £919 | £684 |
| 3.0 | 3,258 kWh | £858 | £638 |
| 3.5 | 2,793 kWh | £735 | £547 |
| 4.0 | 2,444 kWh | £643 | £479 |
| 4.5 | 2,172 kWh | £572 | £425 |
Green beats a gas boiler at £1,025 a year (including the gas standing charge).
What affects SCOP
- Flow temperature. The cooler the water sent to your radiators, the higher the efficiency. This is the biggest factor.
- Radiator size. Bigger radiators or underfloor heating let the system run cooler.
- Insulation. A home that holds heat needs less of it, at lower temperatures.
- Setup. Weather compensation and steady running beat short hot bursts.
Ask your installer for the design SCOP and flow temperature in writing before you sign. Then put that SCOP into the calculator.
FAQs
What is a good SCOP for a heat pump?
In UK homes, around 2.8 is typical, 3.5 is good and 4 or more is excellent. At current prices you need about 2.8 to match a gas boiler on a standard tariff.
What is the difference between COP and SCOP?
COP is efficiency at one moment in set conditions. SCOP is the average over a whole heating season, including cold days, so it is the better guide to running costs.
How can I improve my heat pump’s SCOP?
Lower the flow temperature, use weather compensation, fit larger radiators or underfloor heating where needed, and avoid switching the system on and off in short bursts.
Run your heat pump on cheaper electricity
Cosy Octopus has three cheap windows a day, priced 51% below its day rate. Switch through our referral link and you also get £50 credit.
Get an Octopus Quote + £50 Credit →You need a heat pump and a smart meter. Link checked 5 October 2026.