Heat pump guide

The operation of a heat pump is based on a cooling cycle in which the temperature of the extracted thermal energy is raised to the required level. In practice, electric scroll or piston compressors are used, which work efficiently and are hardly audible.

What is the annual power consumption?

What is the annual power consumption? Depending on the heat source, a heat pump requires approximately 20 to 25 percent electricity as drive energy to generate heat from the air, the ground and water. This means that the heat pump needs about two kilowatt hours of electricity to produce ten kilowatt hours of usable heat. Several factors play a role in the annual electricity consumption, the most important of which are:

  • The type of heat pump
  • The seasonal coefficient of performance (SCOP)
  • The annual heating required

Power consumption depends on type of heat pump

Depending on which heat source is used, different electricity costs will arise. In principle, air-water heat pumps consume more electricity than brine-water and water-water heat pumps. How the heat pumps differ in detail is explained in the section Types of heat pumps.

The SCOP as an important characteristic value in the calculation

In order to roughly determine the electricity consumption of a heat pump, the seasonal performance factor (SCOP) must be available. This can in turn be determined using the Coefficient of Performance (COP). The latter represents the instantaneous ratio of the heat pump drive energy to the useful heat generated. To obtain the SCOP, the average of all COPs occurring during the year is therefore calculated.

The energy status plays an important role

In addition to the annual performance factor and the type of heat pump, the heat requirement and the annual heating performance are a decisive factor in electricity consumption. How high the heat demand is, in turn, depends on the type and the energy status of the building as well as on the usage behaviour of all residents. Last but not least, it makes a huge difference whether the heat pump is only responsible for heating or also for hot water. A blanket statement is therefore not possible. If all these factors are present, the annual electricity consumption can be roughly calculated using this formula:

Power consumption = heating capacity : SCOP x operating hours

In practice, this means that if a brine/water heat pump with 10 kilowatts and a SCOP of 4.0 runs for 2,000 hours a year, then it requires 5,000 kilowatt hours (10 / 4.0 * 2,000 = 5,000 kWh). If system owners want to calculate the annual electricity costs, they can multiply the sum by the kilowatt price.

The picture shows the most popular Viessmann heat pump models as part of the heat pump guide.

The Viessmann heat pump product range

How can I reduce my energy consumption?

A large part of the energy required in the home is used for heating and DHW. By replacing their obsolete boilers with a heat pump or a hybrid system, homeowners can reduce energy consumption by up to 30 percent. If, in addition to heating modernisation, they also take additional measures such as hydraulic balancing or the replacement of thermostats, their success will improve even further. To further minimise energy consumption, the radiators should fit the heating system as accurately as possible. Read more about this in the section Buying a heat pump.

Can I operate a heat pump with underfloor heating?

Underfloor heating is a type of surface heating that emits heat to the room via radiation. In this way, the thermal energy is distributed evenly over large surfaces and only emits its energy when it reaches solid surfaces such as walls or people. Thanks to the large surface area, underfloor heating with flow temperatures of around 35 degrees Celsius is sufficient.

In comparison, a radiator requires temperatures of up to 70 degrees Celsius. As the efficiency of a heat pump continues to increase the smaller the difference between the heat source and the flow temperature of the heating system. Operation with underfloor heating is not only possible, it is even advisable. Because in this combination the heat pump achieves the highest possible efficiency. Heat pumps in bivalent operation or hybrid heat pumps are recommended for radiator systems with higher temperatures.

Does the heat pump require maintenance?

A heat pump is considered particularly low-maintenance during operation, as only a few moving parts are installed and all components are generally optimally matched to one another. In order to ensure a permanently safe and economical operation, it is nevertheless advisable to appoint a specialist for the yearly inspection. He takes a closer look at the system, determines the current status and, if necessary, optimises all control parameters in order to permanently guarantee the efficiency of the heat pump. The best time for an inspection are the warm months, as the heating and hot water requirements during this period are very small.