28 September 2021

What is COP?

ASHP Winter

Every day more and more heat pumps are coming to market and they all claim to be the best. But how can we determine whether the manufacturer’s claims can deliver efficient performance in the real world? A good place to start is by having a look at the heat pump’s COP.

COP stands for ‘Coefficient of Performance’ and provides a quick indication of a heat pump’s efficiency. When it comes to heat pumps, COP is essentially useful heat output divided by electrical power input. The higher the COP value, the less energy the pump will use to generate heat.  

Outdoor air always contains heat energy even when it’s below freezing. To be able to maintain a constant energy output to heat a home the compressor must work harder to raise the temperature of the gas and the fan must blow more air through the evaporator to extract the same energy as it did at temperatures above freezing. You can find out more about how a heat pump works here.

As mentioned, the COP is a ratio between the electrical energy consumed and the thermal energy given by the heat pump. In the case of a standard electrical heater, 1kW of energy is consumed and 1kW of energy is added to the room. The beauty of the heat pump is that the electricity provided to the heat pump works to move energy from the air to inside and allows for efficiencies greater than 100% usually between 300% and 500%.

Modern heat pumps are achieving COP values of 4-5 which means that if a house demands 4kW of heating energy only 1kW of electric energy is being consumed to provide the required amount to heat the home. A major pitfall for heat pumps is that the weather plays a pivotal role on the COP value and can fall significantly when outdoor temperatures drop below 0C.

A heat pump with a higher COP might cost more initially but will pay for itself in the long run.

If you have questions about COP or would like to discuss the subject in more detail, please feel to participate in this dedicated COP forum.

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