About Coefficient of Performance (COP)
COP stands for ‘Coefficient of Performance’. This is a ratio with no units, basically indicating the amount of energy required to run the compressor, compared with the amount of energy being produced by the heat pump, to heat the water.
Industry Standard Testing (EN14511) for air source heat pumps is carried out at an air temperature of 7oC and a water temperature of 35oC. Standard testing, carried out to EN14511 establishes a benchmark COP at a particular ambient and circuit water temperature. This is 7oC for ambient air and 35oC for water flow temperature.
For example, the Grant Aerona 6.5kW ASHP model produces a COP of 4.1, when tested to this level. This means for every kilowatt (kW) of energy used to run the Aerona, 4.1kW of energy is being given to the heating system in return.
All air source heat pumps will have a decrease in output if the air temperature is cooler than those test conditions. This is also true if the system water temperature is raised to a higher temperature. It is therefore vital that an accurate heat loss calculation is carried out to ensure the sizing of the heat pump is correct. Not surprisingly, if the air temperature is higher, or system water temperature is lower, an increase in output can occur.
