Heat pump COP (Coefficient of Performance) measures efficiency at a single outdoor temperature, while SCOP (Seasonal Coefficient of Performance) gives a more realistic annual average across the UK heating season. The Energy Saving Trust says a typical air source heat pump has a SCOP of around 3.2, meaning it produces 3.2 kWh of heat for every 1 kWh of electricity used (Energy Saving Trust, 2026). This is the figure to use when estimating your annual running costs.
COP is a snapshot. It tells you the heat pump’s efficiency at one specific outdoor temperature, usually +7°C. SCOP averages efficiency across the full range of outdoor temperatures your heat pump will encounter over a year, including colder winter days when efficiency drops. The UK government’s Boiler Upgrade Scheme requires a SCOP of at least 2.8 for air source heat pumps to qualify for the £7,500 grant (GOV.UK, 2026). Manufacturers list both figures, but SCOP is the reliable guide for real-world performance.
SCOP is the number that matters for running costs
Your annual heating bill depends on SCOP, not COP. A heat pump with a COP of 4 at +7°C might drop to a COP of 2.5 at -2°C. SCOP averages these out. The UK’s average winter temperature is around 4-5°C, so the SCOP reflects typical conditions. For example, a heat pump with a SCOP of 3.2 will use roughly 3,125 kWh of electricity to deliver 10,000 kWh of heat annually. The Energy Saving Trust says a SCOP of 3.0 or higher is good for air source models (Energy Saving Trust, 2026). Ground source heat pumps typically have higher SCOPs, often 3.5 to 4.5.
COP is useful for comparing performance at one temperature
COP helps you compare how different heat pump models perform at the same test condition, typically +7°C. Manufacturers must quote COP under standard test conditions set by the European heat pump standard EN 14511. However, two heat pumps with the same COP at +7°C can have very different SCOPs because of how they handle defrost cycles and part-load operation. The Microgeneration Certification Scheme (MCS) requires SCOP data for certification (MCS, 2026). Always check SCOP first, then look at COP to understand performance at the specific outdoor temperature you experience most often.
Both figures are required for heat pump efficiency labels
UK energy labels for heat pumps show both COP and SCOP. The label includes a seasonal space heating energy efficiency class from A+++ to G. A SCOP of 3.2 roughly corresponds to a 120% efficiency class (A+ on old labels). The label also lists COP at +7°C and at +2°C. The UK government’s Standard Assessment Procedure (SAP) uses SCOP to calculate a home’s Energy Performance Certificate (EPC) rating (GOV.UK, 2026). When comparing heat pumps, look for the seasonal efficiency class and SCOP value, these give the truest picture of how the system will perform in your home.
A worked example
A typical 1930s semi-detached house in Manchester with a 8 kW air source heat pump and a SCOP of 3.2 would save roughly £395 per year compared to a gas boiler at current energy prices. After the £7,500 Boiler Upgrade Scheme grant, the upfront cost comes to approximately £5,500. The Energy Saving Trust confirms that a SCOP of 3.2 is a realistic benchmark for modern heat pumps in UK homes. The 0% VAT rate on heat pumps, running until March 2027, reduces the installation cost further. Over 25 years, the total savings on energy bills would reach around £9,875, making the investment pay for itself within 14 years. This calculation assumes a gas boiler efficiency of 90% and a gas price of 6.5p per kWh versus an electricity price of 15p per kWh. The actual payback period depends on your home’s insulation levels and heating patterns.
| Item | Figure |
|---|---|
| Upfront cost after grants | £5,500 |
| Yearly savings | £395 |
| Payback period | 14 years |
| 25-year lifetime savings | £9,875 |
What homeowners often get wrong
The most common mistake is comparing a heat pump’s COP to a gas boiler’s efficiency without accounting for the seasonal variation in performance. This leads to unrealistic expectations about running costs.
- Using the COP number to estimate annual bills Many homeowners see a COP of 4.5 on the manufacturer’s spec sheet and assume that applies all year. The reality is that the SCOP is typically 25-30% lower at around 3.2, meaning annual running costs are about 40% higher than the COP-based estimate. This can lead to a £200 per year budgeting error.
- Ignoring the impact of poor insulation on SCOP A common belief is that a heat pump’s SCOP is fixed once installed. In fact, a draughty home forces the heat pump to run at higher flow temperatures, which drops the SCOP by 0.5 to 0.8 points. This can add £150 to £300 to your annual heating bill and may void the warranty if the system cannot maintain the required temperature.
- Thinking a higher COP always means a better heat pump Some homeowners choose a model based solely on its COP at +7°C. The better metric is the SCOP at -2°C, because the UK experiences many cold days. A heat pump with a COP of 4.5 at +7°C but a SCOP of 2.8 at -2°C will cost £180 more per year to run than one with a COP of 3.8 at +7°C and a SCOP of 3.1 at -2°C. Check the SCOP value at low temperatures, not just the headline figure.
Quick reference
- A typical air source heat pump in the UK has a SCOP of 3.2, meaning it produces 3.2 kWh of heat for every 1 kWh of electricity used.
- The Boiler Upgrade Scheme requires a minimum SCOP of 2.8 for air source heat pumps to qualify for the £7,500 grant.
- You can check a heat pump’s SCOP on the MCS database at mcscertified.com before buying.
- Every 0.1 increase in SCOP saves roughly £45 per year on a typical 8 kW heat pump installation.
- Never use the COP figure for annual cost calculations, always use the SCOP to avoid overestimating savings by up to 40%.
Frequently Asked Questions
COP measures efficiency at a single outdoor temperature, while SCOP averages across the UK heating season. The Energy Saving Trust says a typical SCOP of 3.2 is the figure to use for running costs.
SCOP is more important because it reflects real-world annual performance. The UK government's Boiler Upgrade Scheme requires a SCOP of at least 2.8 for air source heat pumps to qualify for the £7,500 grant.
A SCOP of 3.0 or higher is good for air source heat pumps, according to the Energy Saving Trust. A typical model achieves around 3.2.
