What is SCOP?
SCOP is the single number that determines whether a heat pump is cheap or expensive to run.
SCOP (Seasonal Coefficient of Performance) measures how many units of heat a heat pump delivers for each unit of electricity it uses, averaged across a full UK heating season. A SCOP of 3.0 means 3kWh of heat for every 1kWh of electricity. UK installations typically range from 2.5 to 4.0, and Energy Saving Trust recommends aiming for at least 3.52. Every extra point of SCOP cuts your electricity bill directly.
Why SCOP matters
Higher SCOP means lower running costs, and the relationship is direct: a pump with SCOP 4.0 uses 25% less electricity than one rated 3.0, for the same amount of heat delivered (3 ÷ 4 = 0.75, so 25% less). The UK government's Boiler Upgrade Scheme requires installers to submit a design SCOP as part of the MCS certification process1.
In cash terms, at the current Ofgem price cap of 26.11p/kWh (Jul-Sep 2026)4, a medium home with 12,000 kWh of annual heat demand costs about £1,044 a year to heat at SCOP 3.0, or £783 a year at SCOP 4.0. That is a difference of over £260 a year from efficiency alone; use the running cost calculator to check your own numbers.
SCOP vs COP
COP (Coefficient of Performance) measures efficiency at a single outdoor temperature, usually 7°C. SCOP is more realistic because it averages performance across the full range of UK winter temperatures, from around -10°C to +15°C. Always use SCOP, not a single COP figure, when comparing UK heat pumps or estimating a winter bill.
Typical SCOP ratings in the UK
| SCOP | Rating | Notes |
|---|---|---|
| 2.5 | Poor | Oversized or high flow temperature (55°C+) |
| 3.0 | Typical | Common for existing UK installations |
| 3.5 | Good | Well-designed, properly sized, Energy Saving Trust minimum target |
| 4.0+ | Excellent | Low flow temperature (35-40°C), underfloor or oversized radiators |
What affects SCOP
- Flow temperature: the biggest single factor. Lower flow temperature (35-45°C) means higher SCOP; it needs larger radiators or underfloor heating to deliver the same warmth.
- Sizing: an oversized pump cycles on and off frequently, which reduces average efficiency. See our sizing guide.
- Insulation: better insulation allows a lower flow temperature to still heat the home, compounding the benefit.
- Climate: milder UK winters help. Scotland and northern England average slightly lower SCOP than southern England because of colder outdoor temperatures.
Illustrative curve: seasonal efficiency (SCOP) typically falls as flow temperature rises. Based on typical heat pump manufacturer performance data, not a single measured unit; actual curves vary by model. See sources below.
Real-world SCOP vs lab figures
Manufacturer SCOP ratings are lab-tested to EN 14825. Real-world performance can run lower if a system is commissioned with a higher-than-necessary flow temperature. The government's Electrification of Heat Demonstration Project, which monitored live UK installations rather than lab units, found an average measured SCOP of around 2.83. More recent installations tracked on public heat pump monitoring dashboards average higher, closer to 3.5-3.9, which suggests commissioning practice has improved. Ask your installer what flow temperature the system is designed for; it is the single best predictor of where your SCOP will actually land.
- Typical UK SCOP
- 2.5 - 4.0
- EST recommended minimum
- 3.5
- Field trial average (2020-22)
- ~2.8
- Cost saving, SCOP 3.0 to 4.0
- 25% less
Frequently asked questions
Is a higher SCOP always better?
Yes for running cost: higher SCOP means less electricity for the same heat. It usually needs a larger heat emitter (radiators or underfloor) to run at a lower flow temperature, which costs more upfront.
What counts as a good SCOP for a UK heat pump?
Energy Saving Trust suggests aiming for at least 3.5. Many existing UK installations run lower, around 2.8 to 3.0, because flow temperatures were not optimised at commissioning.
Does SCOP change with the weather?
SCOP is already an average across a full UK heating season, so it accounts for cold snaps and mild spells. Efficiency on any single cold day (COP) is lower than the seasonal average.
Related guides
Sources
- GOV.UK / MCS, Boiler Upgrade Scheme: eligibility criteria, accessed 3 Jul 2026
- Energy Saving Trust, Air source heat pumps: costs, savings and benefits, accessed 3 Jul 2026
- Carbon Brief, Factcheck: what it really costs to heat a home in the UK with a heat pump, citing the Electrification of Heat Demonstration Project, accessed 3 Jul 2026
- Ofgem, Changes to the energy price cap between 1 July and 30 September 2026, accessed 3 Jul 2026
Try the calculator: Estimate your heat pump running costs using your home size and SCOP rating.
Last reviewed: 3 July 2026.