In recent years, the heat pump has become increasingly popular on the heating market. For new buildings and building refurbishment, users can expect lower energy costs and environmentally friendly, low-maintenance operation. There is much heated debate as to the degree of efficiency at which heat pumps work. 

The debate arises on the one hand from the conflicting interests of manufacturers, energy providers and fuel suppliers. However, in particular, it illustrates that there is not yet sufficient concrete data available from practical use. Measuring results from test stands are only of very limited relevance for real operation, since the efficiency of the heat pump is much more dependent on the conditions of use than with other heating systems. Thus for example, a condensing boiler is dependent on the lowest possible temperature of the heat distribution in the building. With the heat pump, the temperature level and connection to the environmental heat used also plays a key role. The annual coefficient of performance of a heat pump, as a measure of energy efficiency, can therefore vary significantly from building to building.

The “heat pump efficiency” field test by the Fraunhofer Institute for Solar Energy Systems ISE, supported by the German Federal Ministry of Economics and Technology, now aims to create a clear picture for use in new buildings with low annual heating requirements of between approx. 40 and 100 kWh/m².

Although the research project will not be completed until the summer of 2010, the results of two full measurement years are already available.

The most important findings for borehole heat exchanger and ground collector facilities will be presented below. The results for air source heat pumps will be published separately.