Heat pump

Heat Pump - A heat pump is a heating system that extracts environmental heat from the air, the ground, or groundwater, raises it to a higher temperature using a refrigerant cycle, and transfers this heat to the building’s heating system. It is considered a key technology in the heating transition, as it draws a large portion of the required heating energy from renewable sources and meets the requirements of the Building Energy Act (GEG).

How does a heat pump work?

The basic principle of a heat pump is similar to that of a refrigerator in reverse: A refrigerant evaporates at a low temperature, absorbing heat from the environment in the process; it is then compressed by an electrically powered compressor and transfers the heat thus generated to the heating system via a heat exchanger. The key advantage lies in the ratio of energy input to heat output: Depending on the type and conditions, a modern heat pump generates three to five kilowatt-hours of heat from one kilowatt-hour of electricity.

This ratio is measured as the Annual Performance Factor (APF) and is the most important indicator of efficiency. A COP of 3.5 means that the system generates 3.5 kilowatt-hours of heating energy from one kilowatt-hour of electricity. For economic viability and eligibility for subsidies, the COP should be at least 2.7-in practice, values between 3.5 and 4.5 are often achieved in well-insulated buildings with radiant heating systems.

There are three main types of heat pumps: The air-to-water heat pump is the most commonly installed variant, with a market share of over 80 percent. It extracts heat from the outside air and is comparatively simple and cost-effective to install, as no excavation or well drilling is required. Its disadvantage: Efficiency drops at very low outdoor temperatures. The ground-water heat pump (geothermal heat pump) utilizes the constant temperature of the ground via ground probes or ground collectors and operates with high efficiency year-round, but is significantly more expensive to purchase. The water-water heat pump uses groundwater as a heat source and achieves the highest efficiency ratings, but requires a water rights permit and suitable groundwater conditions.

The cost of a heat pump, including installation, ranges from 15,000 to 30,000 euros, depending on the type. An air-to-water heat pump for a single-family home typically costs 15,000 to 20,000 euros, while a ground-source heat pump system with geothermal boreholes costs 20,000 to 30,000 euros. Additional costs may apply for adapting the heating system, such as replacing radiators with underfloor heating.

Subsidies and GEG Compliance

The heat pump meets the 65-percent renewable energy requirement of the Building Energy Act and is thus one of the key compliance options for homeowners replacing their heating systems. Through the Federal Subsidy for Efficient Buildings (BEG), homeowners can receive substantial grants via KfW: The basic subsidy is 30 percent, the climate speed bonus adds another 20 percent when replacing a functioning fossil fuel heating system, and the income bonus adds another 30 percent for households with an income below 40,000 euros. A maximum of 70 percent of eligible costs is subsidized.

For heat pumps that use a natural refrigerant such as propane, there is an additional efficiency bonus of 5 percent. Eligible costs are capped at 30,000 euros for the primary residence. In practice, the maximum subsidy reduces the net investment cost of an air-to-water heat pump to approximately 5,000 to 8,000 euros-an amount that pays for itself within a few years due to significantly lower operating costs.

Practical Tip for Homeowners in Nuremberg and Franconia

In the Nuremberg metropolitan region, the air-to-water heat pump is the most commonly installed type, as the climatic conditions in Franconia-with average winter temperatures between minus 2 and plus 5 degrees Celsius-are well-suited for this model. For geothermal heat pumps, ground probe drilling is possible in many Nuremberg neighborhoods, but requires approval from the Nuremberg Water Management Office-this may be restricted, particularly in water protection areas such as parts of Erlenstegen or Mögeldorf.

We have observed that properties with heat pumps in the region are achieving an increasingly higher market value than comparable properties with fossil fuel heating. When appraising real estate, we consider the type of heating system as a relevant value factor. Owners planning to sell in the coming years should assess whether modernizing the heating system could disproportionately increase the achievable sale price. Well-insulated buildings from the 1990s or newer are particularly well-suited for retrofitting, while for older, uninsulated buildings, the building envelope should be improved first.

Frequently Asked Questions

Does a heat pump work in older buildings?

Yes, heat pumps generally work in older buildings as well, though efficiency depends crucially on the building envelope and the heating system. A well-insulated older building with radiant heating (floor or wall heating) is ideal. However, a heat pump can also be operated economically with generously sized radiators and moderate flow temperatures of 50 to 55 degrees Celsius. We recommend having a heating load calculation performed by a professional designer before installation.

How loud is an air-to-water heat pump?

Modern air-to-water heat pumps generate a sound level of about 35 to 50 decibels at a distance of one meter during normal operation-comparable to a quiet conversation. The noise is mainly generated by the outdoor unit’s fan. In Bavaria, the emission guidelines of the TA Lärm apply: In purely residential areas, the sound level at night must not exceed 35 decibels at the nearest neighboring building. Therefore, sufficient distance from the property line should be planned during installation.

Is a heat pump worth it in combination with photovoltaics?

The combination of a heat pump and a photovoltaic system is particularly attractive from an economic standpoint. The self-generated solar power can be used directly to operate the heat pump, significantly reducing operating costs. With a battery storage system, the share of self-consumption can be further increased. In practice, homeowners in the sunny Nuremberg metropolitan region can reduce the electricity costs for the heat pump by 30 to 50 percent, resulting in heating costs that are significantly lower than those of any fossil fuel alternative.

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