A heat pump’s COP is a lab test, while its SCOP is the real-world annual average, the difference can mean £200–£400 on your yearly heating bill
If you are comparing heat pumps, you will see two efficiency numbers: COP and SCOP. They are not interchangeable, and using the wrong one can lead to a costly surprise on your energy bill. The direct answer is this: COP is a fixed laboratory result, while SCOP is the real-world annual average that accounts for UK weather, and the gap between them can add £200 to £400 to your yearly heating costs.
COP is a lab test under fixed conditions; SCOP is the real-world annual average. In UK homes, a typical COP of 4.0 drops to a SCOP of around 3.2, which can add £200-£400 to your yearly heating bill. Use SCOP for accurate cost estimates.
- COP is a lab test under fixed conditions (EN 14511).
- SCOP is the real-world annual average for UK homes.
- A typical COP of 4.0 drops to a SCOP of 3.2 in UK climate.
- SCOP is used in SAP for EPCs and Boiler Upgrade Scheme.
- The COP-SCOP gap can add £200-£400 to yearly heating costs.
- A heat pump’s COP is a lab test, while its SCOP is the real-world annual average, the difference can mean £200–£400 on your yearly heating bill
- How COP is measured in a lab, and why it differs from your home
- How SCOP is calculated for the UK climate, the seasonal weighting
- Quick numbers COP vs SCOP for common UK heat pump types
- The direct answer to "Which number should I use COP or SCOP?", always use SCOP for running cost estimates
- How to verify your heat pump’s SCOP, MCS certification and installer obligations
- What the SCOP means for your Boiler Upgrade Scheme grant eligibility
COP stands for Coefficient of Performance. It is the ratio of heat output to electrical input measured under a single, fixed set of test conditions. For example, a COP of 4.0 means for every 1 kWh of electricity the heat pump uses, it delivers 4 kWh of heat. SCOP stands for Seasonal Coefficient of Performance. It is the weighted average efficiency over a full heating season, accounting for variable outdoor temperatures, part-load operation, defrost cycles, and standby losses. Energy Saving Trust states that a typical air-source heat pump might have a COP of 4.0 at 7°C but a SCOP of around 3.2 in a UK climate (Energy Saving Trust, 2026). The SCOP is the figure used in the UK’s Standard Assessment Procedure (SAP) for Energy Performance Certificates (EPCs) (GOV.UK, 2026). It is also the metric that determines eligibility for the Boiler Upgrade Scheme grant (GOV.UK, 2026).
How COP is measured in a lab, and why it differs from your home
The standard test for COP follows EN 14511. It measures heat pump performance at a fixed outdoor temperature (typically 7°C for air-source and 0°C for ground-source) and a fixed indoor return water temperature (often 35°C for underfloor heating or 55°C for radiators) per MCS 007 (MCS 007, 2026). The lab test does not include defrost cycles, standby losses, or auxiliary heater use, all of which reduce real-world efficiency.
COP varies with the temperature lift. This is the difference between the heat source (outside air or ground) and the heat sink (your radiators or underfloor heating). A smaller temperature lift means a higher COP. A COP of 4.0 means for every 1 kWh of electricity, the pump delivers 4 kWh of heat, but SCOP accounts for the fact that this ratio drops in colder weather when the temperature lift is larger. In practice, a heat pump that scores COP 4.0 in a lab may deliver SCOP 2.8 during a cold UK winter.
How SCOP is calculated for the UK climate, the seasonal weighting
SCOP is calculated using a standardised climate profile. For the UK, this is typically the “average” or “colder” climate zone defined in EN 14825 (BS EN 14825:2022, 2026). The heat pump is tested at several outdoor temperatures (e.g., +12°C, +7°C, +2°C, -7°C) and the results are weighted by how many hours the UK typically spends at each temperature.
The SCOP includes the energy used for defrost cycles, standby power, and any backup electric heater that kicks in at very low outdoor temperatures. It is expressed as a single number (e.g., 3.2) and is the basis for the heat pump’s “seasonal space heating energy efficiency” label on the UK Energy Label (GOV.UK, 2026). A higher SCOP means lower running costs. Roughly, divide your annual heating demand in kWh by the SCOP to get the electricity used. For example, a home needing 12,000 kWh of heat per year with a SCOP of 3.0 will use 4,000 kWh of electricity.
Quick numbers COP vs SCOP for common UK heat pump types
The table below shows typical COP and SCOP ranges for common heat pump types, based on MCS 007 published data and the Ofgem price cap typical unit rate of 24p/kWh for January 2026 (Ofgem, 2026). Annual electricity use is calculated for a home with a 12,000 kWh heating demand.
| Heat pump type | Typical COP (at 7°C) | Typical SCOP (UK climate) | Annual electricity use (12,000 kWh home) | Annual running cost (at 24p/kWh) |
|---|---|---|---|---|
| Air-source (standard) | 4.0 | 3.2 | 3,750 kWh | £900 |
| Air-source (high temperature) | 3.5 | 2.8 | 4,286 kWh | £1,029 |
| Ground-source (horizontal loops) | 4.5 | 3.8 | 3,158 kWh | £758 |
| Ground-source (vertical boreholes) | 5.0 | 4.2 | 2,857 kWh | £686 |
Annual electricity use = 12,000 kWh ÷ SCOP. Annual running cost = kWh used × 24p. Source: MCS 007, 2026 and Ofgem, 2026.
Always use SCOP for running cost estimates
For estimating your annual heating bill, use the SCOP, not the COP, because it reflects real UK weather and heat pump behaviour. COP is useful for comparing heat pumps under the same test conditions but is misleading for cost predictions, a COP of 4.5 can drop to an SCOP of 2.8 in a cold winter.
When looking at a heat pump’s datasheet, look for the “SCOP for average climate” figure (often labelled SCOP_avg) and the “seasonal space heating energy efficiency class” (e.g., A+++). Energy Saving Trust gives a rule of thumb: a SCOP of 3.0 or higher is good for an air-source heat pump in the UK (Energy Saving Trust, 2026). If a salesperson quotes only the COP, ask for the SCOP, it is the number that matters for your wallet.
How to read a heat pump energy label
How to verify your heat pump’s SCOP, MCS certification and installer obligations
All heat pumps installed under the Boiler Upgrade Scheme must be MCS-certified, and the MCS certificate includes the declared SCOP (MCS, 2026). The installer must provide you with a “MCS Installation Certificate” that lists the heat pump model and its SCOP, and must register the installation on the MCS database.
You can also check the SCOP on the product’s Energy Label. The label shows the “seasonal space heating energy efficiency” in a coloured class (A+++ to D) and the SCOP in kWh/kWh (GOV.UK, 2026). To look up a specific model, use the MCS product directory or the European Heat Pump Association (EHPA) Keymark database (EHPA, 2026).
If the installer cannot provide a SCOP for the model they propose, it is likely not MCS-certified, and you may lose eligibility for the Boiler Upgrade Scheme grant. Always ask for the SCOP in writing before you sign a contract.
MCS certification explained for homeowners
What the SCOP means for your Boiler Upgrade Scheme grant eligibility
The Boiler Upgrade Scheme (BUS) requires the heat pump to have a SCOP of at least 2.5 for air-source and 2.8 for ground-source (GOV.UK, 2026). The grant amount is £7,500 for both air-source and ground-source heat pumps as of April 2026 and does not depend on the SCOP value beyond the minimum threshold (GOV.UK, 2026).
The SCOP used for BUS eligibility is the “declared SCOP” from the MCS certificate, not a COP from a lab test. If your home’s heat demand is calculated by the installer using SAP or a similar method, the SCOP is used to estimate the electricity consumption and thus the running costs for the Energy Performance Certificate (EPC) (DESNZ, SAP 10.2, 2026). A higher SCOP means lower estimated running costs on your EPC, which can improve your home’s energy rating.
Frequently Asked Questions
COP is a fixed lab test result under ideal conditions, while SCOP is the real-world annual average accounting for UK weather and usage patterns. Energy Saving Trust states a typical COP of 4.0 drops to a SCOP of around 3.2 in a UK climate.
SCOP is more important for real-world performance and costs. It is the metric used in the UK’s Standard Assessment Procedure (SAP) for EPCs and determines Boiler Upgrade Scheme eligibility per GOV.UK.
COP is measured in a lab under EN 14511 at a fixed outdoor temperature (e.g., 7°C for air-source) and fixed indoor water temperature. It excludes defrost cycles, standby losses, and auxiliary heaters per MCS 007.
A good SCOP for an air-source heat pump in the UK is 3.0 to 3.5. Energy Saving Trust notes a typical SCOP of 3.2 in UK climates, while ground-source units often achieve 3.5 to 4.5.
The Boiler Upgrade Scheme uses SCOP, not COP. GOV.UK confirms that heat pumps must meet a minimum SCOP to qualify for the £7,500 grant in 2026.
