Types of heat pumps
Overview & differences
Air, water or geothermal heat pumps - the different types of heat pumps utilise different heat sources. There are also models for indoor and outdoor installation. Depending on the structural conditions, property size and space in the basement or plant room, one system may be more suitable than another. Knowing the differences, advantages and disadvantages will help you choose the right type of heat pump and find the right heating solution for your home.
At a glance
- Types of heat pumps: Air-to-water, water-to-water and brine / water heat pumps differ primarily in the heat source they utilise - be it the ambient air, groundwater or the ground.
- Particularly easy to install: Air source heat pumps do not require any development measures and are therefore also ideal for retrofitting.
- Efficient, but more complex: Groundwater and geothermal pumps require drilling or the installation of collectors.
- Other heat pump types: Air-to-air heat pumps without a water-bearing heating circuit and domestic hot water heat pumps for heating domestic hot water only. Hybrid heating as a combination of heat pump and existing heating system.
- Selection criteria: Climate, building type, property, costs and subsidies determine the right type of heat pump.
The most important types of heat pumps
As a climate-friendly heating solution, heat pumps convert environmental energy into heat - this operating principle is the same for all types of heat pumps. The main difference between them is the energy source from which they obtain their heat.
- The air-to-water heat pump obtains its heat from the ambient air and is particularly flexible to use.
- The brine / water heat pump, also known as a geothermal heat pump, converts the heat from the ground into heating energy and is particularly suitable for properties with sufficient space.
- The water-to-water heat pump uses groundwater as a heat source and impresses with its constant and high efficiency.
The function of heat pumps is explained in detail here.
Air-to-water heat pump in detail
How does an air-to-water heat pump work?
This type of heat pump continuously draws in ambient air via a fan. This is either outside air (for outdoor appliances) or inside air (for appliances installed in the basement). The air source heat pump extracts energy from this air, brings it to a higher temperature level through a compression process in a refrigerant circuit and then transfers it to the heating water.
This even works when the temperature outside falls below 0 °C. For outdoor units in particular, this means that the "heat" of the energy source, i.e. the outside air, is very low. Nevertheless, sufficient heat can be generated. It is only important that the boiling point of the refrigerant in the heat pump is below the outside temperature.
What needs to be considered when installing an air-to-water heat pump?
There are two installation options for this type of heat pump:
- Heat pump as an outdoor unit: The air heat pump is installed weatherproof in front of the building or in the garden.
- Models for indoor installation: The system is installed in a protected location inside the house.
With both versions, it is important to ensure that the airflow is not obstructed. Further development measures are necessary.
Typical areas of application for this type of heat pump are new buildings, but also the retrofitting of existing heating systems, as the air-to-water heat pump is relatively easy to integrate.
Water-to-water heat pump in detail
How does a water-to-water heat pump work?
A suction well pumps groundwater to the heat pump. Its constant temperature is particularly suitable for generating heat. The groundwater heat pump extracts the heat from this water and utilises it for the heating system via the compression process. The groundwater is fed back into the ground via an absorption well.
What needs to be considered when installing a water-to-water heat pump?
The following are necessary for the installation of this type of heat pump
- The construction of wells for water extraction and recirculation
- Access to clean groundwater
- Obtaining permits and fulfilment of requirements
Typical areas of application are properties with good access to groundwater.
Brine / water heat pumps in detail
How does a brine / water heat pumps work?
A brine / water heat pumps requires geothermal probes or geothermal collectors. A liquid, the brine, circulates through these, which absorbs the heat from the ground and feeds it to the heat pump. Within the heat pump, the energy is then utilised for heating by means of a compression process.
What needs to be considered when installing a brine / water heat pumps?
There are two versions of extracting heat from the ground:
- Geothermal probes: Are installed in drill holes about 100 metres deep. Here, the possibility and suitability for drilling on the property are decisive. Regional regulations must also be checked. The advantage: From a depth of around 10 metres, the ground temperature remains constant all year round.
- Geothermal collectors: Are laid in a serpentine pattern at a depth of around 1.5 metres and require more area than geothermal probes. A sufficiently large, unsealed plot of land is therefore required.
Typical areas of application for this type of heat pump are new buildings and properties with sufficient undeveloped land.
Species in comparison
Heat pump type | Air-to-water heat pump | Water-to-water heat pump | Brine / water heat pumps |
|---|---|---|---|
Operating principle | Extracts heat from the ambient air | Utilises groundwater as a heat source | Utilises geothermal energy via geothermal probes or collectors |
Installation site | Indoor or outdoor installation possible | Indoor installation + 2 fountains | Indoor installation + geothermal collectors or geothermal probes |
To be observed during installation | Free air circulation, for outdoor installation: specified distances | Access to clean groundwater, authorisation | Sufficient space on the property for geothermal probes/collectors |
Investment costs | Low to medium | Medium to high | Medium to high |
Operating costs | Moderate, for outdoor units also dependent on outdoor temperature | Low, very efficient | Low, very efficient |
Advantages | Simple installation, no need to drill holes in the ground | Very high efficiency, constant high output | Very high efficiency, long service life |
Disadvantages | Performance drops at very cold temperatures (especially with appliances installed outside) | Authorisation procedure for groundwater required | Boreholes or collectors require space |
Typical areas of application | New construction and refurbishment, also in densely built-up areas | New construction and refurbishment with access to groundwater | New construction and refurbishment with sufficient land |
Funding opportunities | State subsidies and loans possible | Government grants and loans possible | Government grants and loans possible |
Heat pump as an indoor or outdoor unit?
The most commonly installed type of heat pump is the air-to-water heat pump. Thanks to its flexible installation options, it is also suitable for different structural conditions on or in the house.
Outdoor installation: If there is little space in the basement or indoors, outdoor units can be installed flexibly in front of the house or in the garden. However, distances from neighbouring properties and bedrooms must be taken into account due to the noise generated. Note: Weather-resistant materials and a robust housing.
Indoor installation: Air source heat pumps can also be installed inside the building - this installation option is considered to be one of the quietest. The prerequisite for this is, of course, sufficient space in the house. Especially when switching to renewable energies, the room of the old oil heating system or oil tank can be used, for example.
Please note: Stable, solid walls in the installation room
Tip: Volume of outdoor heat pumps
The noise level also plays a role with the different types of heat pumps. This is because the fans of air heat pumps in particular generate noise. But there is no need to worry that an outdoor unit will operate very loudly and disturb neighbours or residents: Thanks to particularly effective sound and vibration damping, heat pumps from KERMI run as quiet as a whisper. The noise level is comparable to the rustling of leaves in the wind.
And if it needs to be particularly quiet, the additional silent mode ensures extra quiet operation. This means that the appliances can usually be installed outside without any further structural measures.
Other types of heat pumps
Air-to-air heat pump: This type of heat pump works in a similar way to an air conditioning system: it extracts heat from the outside air, brings it to a comfortable temperature level and releases it directly into the room via a fan system. Unlike other heat pumps, there is no water-bearing heating circuit and no hot water preparation.
Domestic hot water heat pumps, or drinking water heat pumps - the name says it all: This type of heat pump does not heat rooms, it only heats the drinking water required in the household, for example for showering, washing hands or cooking. Similar to the air-to-water heat pump, it utilises the energy of the room air, outside air or extract air. The domestic hot water heat pump is often used in combination with existing heating systems and enables noticeable energy savings compared to conventional water heaters.
What is hybrid heating?
A hybrid heating system combines a heat pump with a conventional heating system to utilise the advantages of both technologies: The heat pump provides energy-efficient and environmentally friendly heating in mild temperatures, while the conventional boiler kicks in when the outside temperature is very cold.
Advantages of hybrid heating:
- Height flexibility and operational reliability
- Legal protection in extreme outside temperatures, particularly relevant for old buildings
- Utilisation and preservation of existing heating infrastructure
Typical application scenarios:
- Refurbishment of existing heating systems
- Transitional solution on the way to complete heat generation with the heat pump
You can find more information about hybrid operating modes as a supplement to existing heating systems here.
Choosing the right type of heat pump
Ultimately, your individual situation will determine which type of heat pump is the best choice for your home. To summarise, you should keep the following factors in mind:
- Climatic conditions: The milder the climate and the higher the average outdoor temperatures, the more suitable an air-to-water heat pump is.
- Building type and insulation standard: All heat pump types are suitable for new builds. For older buildings, the air-to-water heat pump is often the simplest solution due to the retrofitting options.
- Structural conditions: The availability of land area, access to groundwater or geothermal energy influences the choice. Water-to-water and brine / water heat pumps often offer the higher efficiency here, but require appropriate conditions.
- Cost-effectiveness: Air-to-water heat pumps generally have lower investment costs, as no complex development measures are required, but can incur higher operating costs.
- Subsidy programmes and legal framework conditions: There are funding opportunities for all three types of heat pumps, some of which are linked to specific requirements.
FAQ
Buy a KERMI heat pump
We attach great importance to the highest quality and flawless installation of our products. That is why we sell KERMI heat pumps exclusively via the three-stage sales channel. This ensures that you not only receive a premium product, but also benefit from the best possible advice, planning and professional installation. Your qualified local specialist partner is your direct contact and ensures the optimal integration of our efficient and sustainable heating solutions into your home.