Heat Pump COP UK: How Refrigerant Affects Efficiency

What Is COP and Why Does It Matter?

COP (Coefficient of Performance) is the measure of a heat pump efficiency — the ratio of heat output to electrical energy input. A COP of 3 means the heat pump delivers 3 kW of heat for every 1 kW of electricity consumed. For UK homeowners and businesses, COP directly affects running costs and carbon footprint.

The refrigerant inside the heat pump plays a significant role in determining achievable COP, particularly at low outdoor temperatures — which are common in UK winters.

How R32 Improves COP Versus R410A

R32 has superior thermodynamic properties to R410A in several key areas:

• Higher volumetric heating capacity: R32 delivers more heating energy per litre of gas circulated, allowing smaller compressors to achieve the same output
• Better performance at low ambient: R32 maintains higher COP at low outdoor temperatures compared to R410A — a significant advantage in UK winters
• Lower charge weight: Reduces internal pressure losses in the refrigerant circuit

These properties explain why major heat pump manufacturers moved from R410A to R32 — better seasonal efficiency ratings (SCOP) are achievable with the same compressor technology.

How Correct Refrigerant Charge Affects COP

An incorrectly charged heat pump — whether overcharged or undercharged — will operate at lower efficiency than its rated COP:

• Undercharge: Low suction pressure, high superheat, reduced capacity and COP
• Overcharge: High condensing pressure, liquid slugging risk, reduced COP and compressor stress

Correct charge by weight, verified with superheat and subcooling measurements, is essential for rated performance.

For R32 heat pump charging work, our R32 9 kg cylinders are the trade standard. Browse our full refrigerant range.