Heat Pump COP Comparison by Brand

The coefficient of performance (COP) is the single most important number when comparing heat pump efficiency. It tells you how many units of heat the system delivers for every unit of electricity consumed. A COP of 4.0 means you get four kilowatt-hours of heat for every kilowatt-hour of electricity — essentially 400% efficiency.

This guide provides a comprehensive, data-driven comparison of COP values for every major heat pump brand available in the UK. We compare performance at different outdoor temperatures and flow temperatures so you can see exactly how each model performs in real-world conditions.

Understanding COP and SCOP

What Is COP?

COP is measured at a specific set of conditions — a particular outdoor air temperature and a particular water flow temperature. The standard test condition used across Europe is A7/W35, which means 7°C outdoor air temperature and 35°C water flow temperature. This represents a mild UK winter day with a low-temperature heating system (underfloor heating or oversized radiators).

What Is SCOP?

SCOP (Seasonal COP) is the average COP across an entire heating season, accounting for varying outdoor temperatures. It is a more realistic measure of real-world performance than a single COP number. SCOP values are typically 10 to 20% lower than the peak COP at A7/W35.

Why Flow Temperature Matters

The flow temperature — the temperature of water sent to your radiators or underfloor heating — has an enormous impact on COP. A system running at 35°C (suitable for underfloor heating) will achieve a COP 40 to 60% higher than the same system running at 55°C (often needed for undersized radiators).

This is why radiator sizing and insulation matter so much. They determine the flow temperature needed, which determines your COP, which determines your running costs.

Complete COP Comparison Table

The following table compares COP values for the most popular heat pump models in the UK market. All data is sourced from manufacturer datasheets and MCS product directories. We have standardised the comparison to a mid-range output model (6 to 10kW) from each brand.

COP at Different Outdoor Temperatures (W35 — Low Flow)

COP at Different Outdoor Temperatures (W55 — High Flow)

If your home uses standard radiators without upgrading, you may need a flow temperature of 55°C. This significantly reduces COP across all brands:

What the Data Tells Us

Vaillant Leads on Efficiency

The Vaillant aroTHERM plus consistently tops the efficiency charts, particularly at the standard A7/W35 test condition. Its SCOP of 5.08 is the highest of any domestic air source heat pump widely available in the UK. The R290 refrigerant contributes to this advantage, particularly at lower outdoor temperatures.

Mitsubishi Excels in Cold Weather

Whilst the Mitsubishi Ecodan does not lead at mild temperatures, it holds up remarkably well at -7°C and -15°C. Its flash injection technology maintains capacity and efficiency when other brands drop off more sharply. For properties in cold climates, this is a significant advantage.

Samsung Offers the Best Value per COP Point

When you factor in purchase price, the Samsung EHS Mono delivers more COP per pound spent than any other brand. Its efficiency at A7/W35 is only marginally behind Daikin, at a significantly lower price. For budget-conscious buyers, this makes Samsung the value leader.

Flow Temperature Has a Bigger Impact Than Brand

Perhaps the most striking finding from this data is that the difference between W35 and W55 flow temperatures (within the same brand) is far larger than the difference between the best and worst brand at the same flow temperature. Reducing your flow temperature from 55°C to 35°C improves COP by 50 to 70% — roughly equivalent to upgrading from the cheapest brand to the most expensive.

This means investing in properly sized radiators or underfloor heating delivers a bigger efficiency improvement than choosing a premium brand. The ideal approach, of course, is to do both.

How COP Affects Your Electricity Bills

To translate COP into real money, consider a typical 3-bed semi needing 12,000kWh of heat per year:

The table illustrates two critical points. First, a heat pump with oversized radiators at W35 costs significantly less to run than a gas boiler. Second, a heat pump forced to run at W55 can actually cost more than gas — which is why proper system design is so important.

Real-World vs Lab COP

Manufacturer COP values are measured under controlled laboratory conditions. Real-world performance is typically 10 to 25% lower due to:

• Defrost cycles: Energy used for defrosting reduces effective COP by 5 to 15%.
• Cycling losses: Start-up and shutdown inefficiencies, particularly with fixed-speed compressors.
• Hot water production: Heating water to 50 to 55°C for domestic hot water reduces average COP.
• Pump and control energy: Circulation pumps, fans, and controls consume electricity not always included in lab COP.
• Installation quality: Poor pipe insulation, incorrect refrigerant charge, or wrong settings can reduce COP significantly.

The Energy Saving Trust's monitoring data shows that real-world SCOP values in UK homes typically range from 2.5 to 3.8, with the best installations achieving 4.0 or above. The gap between lab and real-world performance is narrowing as installation standards improve.

How to Maximise Your COP

• Reduce flow temperature: Use underfloor heating or oversized radiators to run at 35 to 40°C.
• Insulate thoroughly: Lower heat loss means lower flow temperatures and better COP.
• Use weather compensation: Let the heat pump adjust flow temperature based on outdoor conditions.
• Avoid short cycling: Use a buffer tank if needed to ensure smooth operation.
• Service annually: Clean filters, check refrigerant charge, and verify settings.
• Monitor performance: Use the heat pump's app or an energy monitor to track COP and identify issues early.

Frequently Asked Questions

What is a good COP for a heat pump?

At the standard A7/W35 test condition, a COP of 4.0 or above is good, and 4.5 or above is excellent. In real-world seasonal terms (SCOP), anything above 3.0 means the heat pump is delivering meaningful savings compared to a gas boiler.

Why does COP vary so much between brands?

Compressor technology, heat exchanger design, refrigerant choice, and control software all affect COP. Variable-speed inverter compressors consistently outperform fixed-speed units. R290 refrigerant tends to deliver higher COP than R32, particularly at low outdoor temperatures.

Does a higher COP always mean lower running costs?

Generally yes, but the relationship depends on your specific installation. A heat pump with a high lab COP but poorly designed heating system may deliver lower real-world SCOP than a mid-range unit in a well-designed system. Installation quality matters as much as the equipment.

How do I find the COP of a specific model?

Check the MCS product directory or the manufacturer's datasheet. Look for COP values at multiple test conditions (A7/W35, A7/W55, A2/W35, A-7/W35) to understand performance across different scenarios. Single-point COP claims without specifying conditions should be treated with caution.

Is SCOP more useful than COP?

Yes. SCOP gives you a seasonal average that better represents real-world performance over a full heating season. COP at a single test point is useful for comparing brands under identical conditions, but SCOP is closer to what you will actually experience.

Do ground source heat pumps have higher COP?

Yes. Ground source heat pumps typically achieve SCOP of 4.5 to 5.5 because the ground temperature remains constant at 8 to 12°C year-round. This consistency eliminates the cold weather COP drop that affects air source systems.