Reality Check · August 2026
Heat Pump SCOP & Running Costs Reality Check
What the real-world UK data shows, and how it supports the conservative assumptions in our calculators.
Quick Answer
The largest UK field trials and the MCS installation database show an average SCOP for air source heat pumps of around 3.4. Homes with underfloor heating often achieve around 3.7. Older properties tend to sit lower; well-insulated newer homes can do better.
Our calculators use conservative figures in this range so the running cost estimates remain realistic for Devon and Cornwall properties rather than optimistic laboratory numbers. That is why the figures sit where they do.
What the public data shows
MCS installation data and the Electrification of Heat Demonstration Project (the largest UK field trial) both point to a mean SCOP of about 3.4 for air source heat pumps in real homes.
- Underfloor heating systems in the trials averaged around 3.7
- Radiator systems averaged closer to 3.2
- Pre-1945 properties averaged around 3.1
- Post-2010 properties averaged around 3.7
Higher figures (4.0+) appear on well-designed systems with good emitters, weather compensation and careful commissioning. They are not the everyday average.
Why the calculator uses conservative figures
Running cost estimates are only useful if they survive contact with a real South West winter and a real older property. Using an optimistic laboratory SCOP would understate the electricity use and overstate the savings.
The calculator therefore works with conservative seasonal figures that sit inside the published field data. For underfloor heating paths the baseline is around 3.7. Radiator paths sit lower. That keeps the planning numbers honest.
What this means for running costs
Electricity unit rates and standing charges change. The calculator uses current typical rates and the conservative SCOP so the annual running cost estimate is a realistic planning figure, not a best-case marketing number.
Actual running costs will still vary with how the house is used, the outdoor temperature, the exact system design and the tariff. The survey and the first year of operation give the true picture.
South West notes
Older solid-wall and small-bore properties common in Devon and Cornwall more often sit toward the lower end of the SCOP ranges unless the emitters and controls are upgraded properly. New builds and well-insulated renovations with underfloor heating more often achieve the higher end. The calculator starts from the conservative side so the figure remains useful across the range of local housing.
See the planning numbers for your home
The free heat pump Passport already uses the conservative SCOP assumptions that sit inside the real-world data. No obligation. Every submission is personally reviewed.
Start heat pump Passport →Frequently asked questions
What is a realistic SCOP for a heat pump in the UK?
MCS installation data and the largest UK field trials show an average SCOP around 3.4. Homes with underfloor heating often achieve around 3.7. Older properties tend to sit lower. Our calculators use conservative figures so the running cost estimates remain realistic.
Why does the calculator use a SCOP of about 3.7 for underfloor heating?
Field data shows underfloor systems commonly achieve around that figure when properly designed. Using a conservative number protects the running cost estimate rather than over-promising.
Will my running costs match the calculator?
The calculator gives a realistic planning figure. Actual costs depend on how the house is used, the outdoor temperature, the exact system design and the tariff. The first year of operation gives the true picture.