Glossary
COP and SCOP: heat pump efficiency ratings explained
Quick definition
COP stands for Coefficient of Performance. It is the ratio of heat output to electrical input at a given moment. A COP of 4.0 means the heat pump delivers 4 kWh of heat for every 1 kWh of electricity it draws. SCOP (Seasonal COP) is the same ratio averaged across a full heating season, accounting for the range of outdoor temperatures the system actually operates at. SCOP is the more useful number for estimating annual running costs.
What does COP tell you?
COP is measured under specific laboratory test conditions defined by the European standard EN 14511. The two most common test points you'll see on devis and product data sheets are:
- A7/W35: outdoor air at 7°C, water flow temperature to the heating circuit at 35°C. This is the standard rating condition for milder climates.
- A2/W35: outdoor air at 2°C, water flow at 35°C. Tests performance in cooler conditions.
- A-7/W35: outdoor air at -7°C, water flow at 35°C. The cold-climate test point, used for systems specified for harsher winters.
COP falls as outdoor temperature drops, because the heat pump has to work harder to extract heat from colder air. An air-water heat pump with a COP of 4.5 at A7/W35 might have a COP of 3.0 at A-7/W35. In PACA, where outdoor temperatures rarely fall far below zero, the heat pump almost always operates in its more efficient range.
Flow temperature also matters: the lower the water temperature the heating circuit runs at, the higher the COP. Underfloor heating systems (typically 35°C) run at lower flow temperatures than older radiator systems (often 60-70°C), which is why heat pumps paired with underfloor heating or well-sized radiators deliver better efficiency than those bolted on to an existing high-temperature radiator circuit.
What does SCOP tell you?
SCOP is calculated under the European standard EN 14825, using reference climate data from test cities representing different European climate zones. The figure quoted on ErP energy labels uses the average climate reference (Strasbourg). In practice, a heat pump installed in PACA (climate zone H3, Mediterranean) will typically achieve real-world seasonal efficiency above the label SCOP, because the Riviera spends very few hours at the extreme cold temperatures that drag the average down.
For a modern air-to-water heat pump at a flow temperature of 35°C in southern France:
- SCOP of 3.5-4.0: acceptable
- SCOP of 4.0-5.0: good to excellent
- SCOP below 3.0: question the system specification or the flow temperature assumption
Why does this matter for running costs?
The running cost of any heat pump depends directly on its SCOP. If your home requires 10,000 kWh of heat per year and electricity costs 0.25 EUR/kWh:
- Electric radiators (SCOP 1.0): 2,500 EUR/year
- Heat pump at SCOP 3.0: 833 EUR/year
- Heat pump at SCOP 4.5: 556 EUR/year
The difference between a SCOP 3.0 and a SCOP 4.5 system is not trivial over a 15-20 year lifespan. Specifying the right system for your heating circuit temperature is one of the most important decisions in the installation.
SEER: the cooling equivalent
If you're looking at a reversible heat pump or split AC system, you'll also see SEER (Seasonal Energy Efficiency Ratio): the seasonal efficiency for cooling. A SEER of 5.0 means 1 kWh of electricity delivers 5 kWh of cooling. The calculation method and climate reference data are the same as for SCOP.
What to look for on a devis
A well-specified quote for a heat pump installation should state:
- The COP at the relevant test condition for your climate (A7/W35 at minimum)
- The SCOP (ErP label class: should be A++ or better for modern air-water systems)
- The design flow temperature for your heating circuit (this directly affects which efficiency figure is relevant)
If the quote only lists the brand and model without efficiency data, ask for the product data sheet. Any reputable installer will provide it.