Heat pump in apartment buildings: Complete 2025 guide
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Stefano Fonseca ist Ingenieur für Energie und Umwelt mit über sechs Jahren Erfahrung in der technischen Gebäudeausrüstung (TGA). Er kombiniert technisches Fachwissen mit einer Leidenschaft für verständliche Kommunikation. Seit mehr als fünf Jahren schreibt er als freiberuflicher Redakteur über erneuerbare Energien und nachhaltiges Wohnen, insbesondere über Photovoltaik und Wärmepumpen.
The heat pump is considered a key technology for climate-friendly heating. But can this also be transferred to apartment buildings? Which systems are suitable, how much does installation cost and what must be considered? This guide provides the most important answers.
Why are heat pumps useful in apartment buildings?
Heat pumps make sense in apartment buildings because they meet the requirements of the Building Energy Act (GEG). They use environmental heat from air, soil or water and thus reduce CO₂ emissions. Since 2024, new heating systems have been required to use at least 65% renewable energy. Heat pumps easily reach this proportion and are therefore eligible for funding.
For owners, the switch is also economically worthwhile. Operating costs are lower than oil or gas. There is also high funding from BEG, which covers up to 70% of investment costs. This significantly increases efficiency and, in addition, real estate value.
Types of heat pumps for apartment buildings
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Which types of heat pumps are suitable for apartment buildings?
Depending on space, construction and heating requirements, different types of heat pumps are suitable for apartment buildings. Each uses a different heat source and has specific technical, approval and investment requirements.
- Air to water heat pump: These systems extract heat from the outside air and feed a central heating system. They are easy to install and are well suited for existing and new buildings. It is important to have a suitable installation location for the outdoor unit. Efficiency decreases in winter, which can be offset by larger buffer tanks.
- brine water heat pump: This solution uses geothermal energy via geothermal probes or area collectors. It offers high efficiency with constant performance, but requires drilling or large outdoor areas. Ideal for larger new construction projects with sufficient plot of land.
- Water-to-water heat pump: Here, heat is extracted from groundwater. This provides maximum efficiency, but requires stable water levels and official approval. The development is complex, but is worthwhile if there is a high and permanent heat requirement.
- Hybrid heat pump: In old buildings with high heat requirements, a combination of heat pump and gas or oil heating can be useful. The heat pump covers the base load; the conventional system kicks in at peak load. This reduces emissions and improves supply security.
The following table shows a direct comparison of the most important characteristics of the types of heat pumps mentioned.
Innovative systems such as ice storage or waste water heat utilization are further options and offer high efficiency. In practice, however, they are only rarely implemented due to high costs, complex planning and approvals.
An ice storage tank uses the heat that is generated when water freezes. In combination with solar thermal energy or air heat, it can supply a heat pump stably all year round. However, such systems require a lot of space and cause high planning costs. This is usually only worthwhile for large new buildings with a long-term operating concept.
Waste water heat pumps are also efficient, as the waste water remains constantly warm even in winter. However, they require special heat exchangers in the pipeline system, a permit from the municipality and high initial investments. For this reason, they have so far only been used in pilot projects or large district solutions.
Centralized or decentralized: Which is more suitable for apartment buildings?
For apartment buildings, a central heat pump system is usually more suitable because it works more efficiently and is easier to maintain. A decentralized solution can still be useful if individual control or flexible retrofitting is paramount.
- Central system: A central large heat pump or a cascade of several heat pumps supplies all apartments together. Heat is generated in a central technical room, which saves space in the residential units. Efficiency is high because the system is evenly loaded. Maintenance can be carried out centrally, which reduces operating costs. This solution is ideal for new buildings or extensively renovated old buildings with a central heating structure.
- Decentralized solution: Here, each apartment has its own heat pump. This variant enables individual control and billing for each residential unit. Installation is often easier for partial renovations when no central solution can be retrofitted. Disadvantages include higher space requirements in apartments, more maintenance costs and lower overall efficiency. However, this variant is well suited for mixed-use buildings or owners' associations with independent energy requirements.
Both variants have advantages and disadvantages:
What are the requirements for a heat pump in an apartment building?
For a heat pump in an apartment building to work efficiently and reliably, structural, technical and legal requirements must be met. In particular, the energy status of the building and the existing heating technology play a central role.
Die most important requirements at a glance:
- Good building envelope: The outer walls, windows and roof should be well insulated. A low heat load is crucial for the heat pump to work efficiently. Unrenovated old buildings with high heat losses are usually unsuitable or require additional systems.
- Low temperature system: Heat pumps work efficiently with flow temperatures below 55°C. Panel heating systems such as floor or wall heating systems are ideal. Low-temperature radiators are also suitable. Classic cast iron radiators or old single-pipe systems can be problematic.
- Enough space: Depending on the system, space is required for an outdoor unit (in the case of air-water), geothermal probes or a technical room. Central systems require additional buffer tanks, hot water tanks and, if necessary, sound insulation measures.
- Reliable power supply: The heat pump requires a separate power connection with sufficient output.
- Hydraulic balancing: The heating circuits must be optimally balanced so that the heat is evenly distributed throughout the building. This is a prerequisite for funding and efficient operation.
- Legal reconciliation: In owners' associations, the installation must be coordinated with all parties involved. Tenants, operating charges and billing issues must also be clarified.
Which legal aspects must be considered?
When it comes to heat pumps in apartment buildings, owners and tenants must comply with different legal requirements. In the case of owners' associations in particular, the approval of all parties involved is crucial.
- Owners association: In a condominium owners' association, a central heat pump may only be installed with the consent of all or a qualified majority. This applies to structural changes to common property, such as pipeline management, technical rooms or outdoor units. Changes to the heating system are generally regarded as “structural changes with significant influence” and therefore require an official resolution in accordance with § 20 WEG. The distribution of investment costs and subsequent settlement must also be clarified in advance.
- Individual owners: If only one individual party wants to install a heat pump, for example as a decentralized solution in their own home, they also need the approval of the owners' association as soon as joint property is affected. This is usually the case, for example with wall openings, power connections or outdoor equipment on the façade.
- Tenant: Tenants may not install a heat pump without permission from the landlord. The landlord decides on the type of heating system and renovation measures. If the central heating system is replaced by a heat pump, the modernization costs may only be apportioned within the legal framework (Section 559 BGB). Tenants can hope to reduce operating costs in return. If rents rise sharply, they have the right to have their profitability checked.
Do you need a permit for heat pumps in apartment buildings?
Whether and which permit is required depends on the type of heat pump, the location of the building and the structural intervention.
- Building permit: In many federal states, a permit is required for outdoor units of air-water heat pumps, especially if they are installed on the façade, in the front garden or on the roof. The state building regulations provide the framework here. Even the Distance to neighboring property must be complied with.
- Authorization for geothermal energy: For brine-water heat pumps with geothermal probes, drilling is required, which requires a water permit in accordance with the Water Resources Act (WHG). The responsible Lower Water Authority is examining possible risks to groundwater.
- Wastewater heat and groundwater: Systems that access wastewater or groundwater are also subject to approval. There is a need for a water permit procedure, which is regulated differently from region to region.
- Heritage protection and design requirements: In areas with special protection status, such as listed facades or ensemble protection, additional permits are required. Municipal development plans can also impose restrictions.
- Proprietary consent: In homeowners' associations, regardless of the building law side, a resolution of all co-owners is required if joint property is changed.
How much does a heat pump cost for an apartment building?
Depending on the system and size of the building, a heat pump in an apartment building costs between 30,000 and 120,000 euros. Air-water systems are the cheapest, geothermal and groundwater solutions are significantly more expensive but more efficient. Additional installation costs arise due to storage, piping and control technology. Decentralized solutions cost per apartment.
The following is a cost comparison for an example with 6 residential units:
What are the operating costs for a heat pump in an apartment building?
The operating costs for a heat pump in an apartment building are on average 3,000 to 8,000 euros per year. Of this, 2,500 to 7,000 euros are due to electricity costs and 500 to 1,000 euros to maintenance of central systems. For decentralized systems, maintenance is around 150 euros per apartment.
How is a heat pump in an apartment building billed?
The billing of a heat pump in an apartment building depends on whether it is a centralized or decentralized system. Consumption recording, electricity purchase and ancillary cost levy are decisive.
- Central system: The heat pump supplies all residential units together. Electricity consumption is recorded via a central meter and passed on to tenants or owners as operating costs (Section 556 BGB, Heating Costs Ordinance). Heating costs are billed based on consumption using heat meters or heating cost allocators in every apartment. Maintenance costs are also included in the annual utility bill.
- Decentralized system: Each apartment has its own heat pump with a separate electricity meter. The respective user bears the electricity costs directly through their electricity contract. There is no need for a central heating bill, as each residential unit works independently. Maintenance costs are charged individually and are to be borne by the respective owner or tenant.
What funding is available for heat pumps in apartment buildings?
Both subsidies and low-interest loans are available for heat pumps in apartment buildings. The most important programs come from KfW and BAFA. Depending on the measure and initial situation, up to 70% funding is possible.
KfW funding for apartment buildings
The most important funding is Subsidy No. 458 from Federal Funding for Efficient Buildings (BEG). It supports the replacement of an old heating system with a climate-friendly heat pump. In the case of apartment buildings, the amount of eligible costs depends on the number of residential units: Up to 30,000 euros are set for the first residential unit, 15,000 euros for the second to sixth residential unit and 8,000 euros from the seventh residential unit onwards. With an air-water heat pump in an eight-party house, up to 121,000 euros in eligible costs would therefore be possible — of up to 70% of which, depending on the bonus share, as a subsidy.
In addition, the KfW with loan No. 359 a low-interest promotional loan with a repayment subsidy. The application must be submitted before the start of the measure and requires confirmation from an energy efficiency expert.
BAFA funding and other programs
The Federal Office of Economics and Export Control (BAFA**) ** also promotes heat pumps as part of BEG individual measures. In addition, exist regional funding programs individual countries or cities that support heat pumps in larger residential buildings. An alternative is the tax restructuring bonus (§ 35c EStG), which allows up to 20% of investment costs to be claimed for tax purposes over three years.
important: A combination of KfW and BAFA funding is generally not possible, but it is possible with regional programs or tax depreciation. Expert advice is recommended for optimal funding.
What output for heat pump in apartment buildings?
For an apartment building, the recommended heating output is 40 to 60 watts per m² of living space. At 600 m², the demand is 24 to 36 kW. As a result of the simultaneity factor, actual performance is often lower. Peak loads can be covered with buffer tanks or additional heating. The exact dimensioning is carried out by a Heat load calculation in accordance with DIN EN 12831.
Is a heat pump worthwhile in an apartment building?
A heat pump is worthwhile in apartment buildings if the building is well insulated and the heating technology is suitably designed. It reduces operating costs in the long term, meets climate requirements and benefits from attractive subsidies — particularly for new buildings or energy-efficient existing buildings.
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