COP
Coefficient of performance: heat delivered divided by electricity consumed at a specific operating condition. A COP of 3.5 means three and a half units of heat for each unit of electricity, and the figure falls as outdoor temperature drops.
Also called coefficient of performance
What is COP?
COP is heat delivered divided by electricity consumed at one operating condition, as a plain ratio. A COP of 3.5 means three and a half units of heat for every unit of electricity used.
COP: how it works
Because a heat pump moves heat rather than generating it, the heat it delivers exceeds the electricity it consumes, and the ratio between the two is the COP. The work the compressor has to do depends on the temperature lift, so a COP quoted at 7 C outdoor air and 35 C flow will be higher than the same machine at minus 7 C outdoor air and 55 C flow.
Where you meet the term
- On a heat pump data sheet, as a table of COP values at several outdoor and flow temperature combinations.
- In a design conversation, where lowering the flow temperature is justified by the COP it buys back.
- In monitoring data, where a measured in-situ COP is compared against the data sheet.
How to check it
- Read the conditions beside the number. A COP is only meaningful with its outdoor temperature and its flow temperature stated. Two COPs at different conditions are not comparable. Owner check
- Compare measured performance against the matching table entry. Monitoring gives an in-situ figure. Comparing it with the data sheet entry for the same conditions is what makes it diagnostic. Technician
Figures you will see
| Condition | Figure | What it tells you |
|---|---|---|
| Meaning of the number | COP 3.0 | Three units of heat delivered for one unit of electricity consumed |
| Direct electric heating for comparison | COP 1.0 | One unit of heat per unit of electricity, the ceiling for resistance heating |
| Relationship to EER | EER divided by 3.412 | Converts the cooling rating into the same dimensionless form |
COP: what it is not
- A COP is not a fixed property of a machine. It is a reading at stated conditions, and it moves as those conditions move.
- A COP above one is not a violation of anything. The heat is moved from outside rather than created from the electricity.
- COP and SCOP are not interchangeable. One is a point, the other is a season.
COP questions
What is a good COP?
It depends entirely on the conditions quoted. A figure at mild outdoor temperature and low flow temperature will look strong and tell you little about performance on the coldest day, which is why data sheets publish a table.
Why does COP fall in cold weather?
The compressor has to lift heat across a wider temperature gap, which takes more work per unit of heat moved. That is the same reason a lower flow temperature raises COP.
How is COP different from SCOP?
COP is a single operating point. SCOP averages across a defined heating season and climate profile, which is what the European product label quotes.
Where this definition comes from
Written from government guidance material held in the HVAC Bench evidence record. Where a document limits a definition to certain models, that limit is repeated here rather than generalised across a brand.
- Energy label and ecodesignThe European framework behind SCOP, seasonal space heating efficiency, and the product energy label.
- Heat Pump SystemsConsumer-facing explanation of air source, ductless, and geothermal heat pump operation and efficiency metrics.