Coefficient of performance of a ground-coupled heat pump

To assess the energetic efficiency of the heat pump process, the ratio of the available useful heat produced by the system is compared to the energy that must be fed into the system. A distinction is made between two different characteristic numbers: coefficient of performance (COP) and Energy Efficiency Ratio (EER).

The coefficient of performance, on the one hand, describes the relationship between the energy produced in the form of heating output (kWh) and the electrical input (kWh) into the system; including all components during a specified period of time (generally this is a year; annual coefficient of performance). This is the best method to assess the energetic quality of a system.

The Energy Efficiency Ratio (EER), on the other hand, gives a figure to the relationship of the heating performance (kW) and the required power (kW) of the heat pump under specific operating conditions. It characterises the efficiency of the heat pump at a specific point in time under defined framework conditions, e.g. the flow heat. Thus the performance output is only a momentary value.

Coefficient of performance (COP) and Energy Efficiency Ratio (EER)

Both values, in essence, depend on the difference in temperature between the source of heat and the heating system that needs to be overcome. They increase, for example, if the temperature of the heat source is high and the flow heat is low in the heating system. The annual coefficient of performance is also influenced by the technical tuning of system components, the amount of water heating in comparison to the total heating requirement, as well as consumer behaviour.

Modern heat pumps that are operated with a thermowell system and a low-temperature heating system today achieve an annual coefficient of performance of 4, i.e. they produce four times as much heat as they require work to generate this heat.

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