Currently, the most common heat pumps on the market use air as a heat source, which makes them more vulnerable to low outdoor temperatures in winter than brine/water heat pumps. However, the advantages of more stable ground temperature with brine/water heat pumps do not compensate for the significantly higher costs of building a ground collector. In fact, an air heat pump does not require the construction of a heat source, as this is provided by the factory-installed evaporator with fan. With a brine/water heat pump, on the other hand, a ground collector must be built, and any design errors (e.g. incorrectly calculated heat output of the ground, pipe diameter too small, pipes laid too close together, etc.) can significantly increase electricity consumption and, in extreme cases, lead to a failure of the heat pump.
Another aspect that influences electricity consumption is the type of heat sink, which is usually the water-based heating system. The greater the difference between the lower and upper heat sources, the more electricity the heat pump needs to heat the building. Therefore, a heat pump that feeds a classic radiator system consumes more electricity than a low-temperature underfloor heating system. Designs available on the market with multi-stage steam injection or the R290 refrigerant significantly improve the performance of heat pumps in conjunction with classic radiators. Nevertheless, it is better to opt for surface heating systems as early as the construction phase of a house in which a heat pump is planned, as they always guarantee the lowest electricity consumption.

A key factor that influences the efficiency of heat pumps is the type of compressor used in the refrigeration system. Heat pumps with inverter compressors enable the heating output to be continuously adjusted to the building's heat requirements, which results in lower power consumption compared to on/off compressors. These constantly run at maximum power, which results in more frequent, energy-intensive start-ups of the compressor motor, faster icing of the evaporator and higher flow resistances in the refrigeration circuit. In addition, the excess energy generated by on/off compressors must be buffered in the heating system, which requires more space in the boiler room and causes additional storage losses that reduce the energy efficiency of the entire heating system in the building.
Also, the length of the pipes (water pipes in monoblocks or cooling pipes in split units) that run outside the building causes additional heat losses and flow resistance, causing the heat pump to operate with less efficiency.