Heat pump

  • Heat pump

    The superior design of the STIEBEL ELTRON heat pump

    What is a heat pump? That's easy to explain.

    Heat pumps convert energy stored in the air, water or beneath the ground into heating energy. And not only that! Combined with a DHW cylinder, this method of heating also safeguards the domestic hot water supply. The three natural elements mentioned above contain practically limitless supplies of energy.

    STIEBEL ELTRON offers highly efficient heat pumps for heating, domestic hot water heating and cooling that are suitable for for every type of home and installation space – new build or modernisation project, indoor or outdoor installation, every requirement is catered for. Engineered in Germany.

    Your heat pump – questions and answers:

    How a heat pump works

    Heat pumps are thermodynamic heating systems. They can be used to convert energy from the environment into heat for your home. First, the heat energy present in water, the ground, outdoor air or extract air is transferred to a refrigerant via a heat exchanger (evaporator). With the aid of a compressor, the refrigerant boosts this energy to a higher temperature level, making it suitable, via another heat exchanger (condenser), for the heating system or DHW heating.

    Depending on the energy source, up to five parts environmental energy can be converted to heating energy for one part of electrical energy used. The environmental energy in the form of a temperature of -20 °C to +35 °C (air) must be brought to a temperature level suitable for heating (DHW). During this process, the water is "pumped" from the low temperature level to the required temperature.

    Did you know: The use of renewables is set to overtake fossil fuels! With the right energy management, you can efficiently generate and store energy for your home. And, with our all-inclusive carefree package, we can help you get the maximum benefit from your heat pump following installation by a qualified contractor. Also worth bearing in mind: we provide a 5 year guarantee on complete systems.

    Heat pump operating modes

    Here, the heat pump is the sole heat generator in the building. This operating mode is suitable for all low temperature heating systems with a flow temperature of up to 55 °C.

    Mono energetic
    In this operating mode, the electric heat pump is backed up by an electric booster heater. This is required, particularly with air-water heat pumps, to provide sufficient heating output at lower outside temperatures. During the longest runtimes in a temperature range down to approx. -7 °C, the heat pump functions as the sole heat generator. In terms of investment and efficiency, it can make sense to use the booster heater as backup during the few hours when the temperature falls below this value.

    Dual mode alternative
    Down to a fixed outside temperature (e.g. 0 °C), the heat pump delivers the entire heating energy. When the temperature falls below this value, the heat pump switches itself off and the second heat generator takes over the heating operation.

    Dual mode parallel
    Down to a certain outside temperature, the heat pump alone delivers the required heating energy. A second heat generator starts at lower temperatures. When the outside temperature falls below the second limit temperature, the heat pump switches off and the second heat generator takes over the entire heating operation. Unlike in dual mode alternative operation, the heat pump provides a much higher proportion of the total annual output.

    The right heat pump

    The WPL 15 ACS
    Positioned and installed outdoors, the WPL 15 ACS air-water heat pump can be used for heating in winter and cooling in summer. The WPL 15 ACS is the right option, even in very densely built-up areas, as its low operating noise will not disturb the neighbours. The WPL 15 ACS is designed for outdoor use. The appliance carries an A++ EU Energy Label and offers cosy warmth from the air, while others turn on their central heating.

    The air-water heat pump can also be used at temperatures well below freezing point – and is always exceptionally efficient. These heat pumps can also be used in modernisation projects due to their high flow temperatures that are achieved even at low outside temperatures.

    The WPL 15 ACS – warms in winter, cools in summer

    The WPL19/24

    WPL19/24 air-water heat pumps, for indoor and outdoor installation, offer maximum flexibility for your home and are an excellent way of meeting demands when modernising detached and two-family houses. With the option of indoor installation, STIEBEL ELTRON is again setting new standards in the efficiency and convenience of inverter-controlled air-water heat pumps.

    Units from the previous WPL 13-23 E series can be replaced very simply, as the casing design and connection concept are the same. Thanks to the state of the art inverter technology, a COP value (indicating heat pump efficiency) of up to 4.12 can be achieved. A COP of between 3 and 5 is regarded as good and efficient. Systems with a heat pump COP value of below 2 are considered uneconomical. This value is derived from the ratio of heating output, the measured kW, to the power consumption of the installed heat pump. Installation without refrigeration certification is no problem thanks to the mono block design, while an integral anti-vibration mount also simplifies the hydraulic connection. These heat pumps are particularly suitable for use in modernisation projects due to the high flow temperatures even at low outside temperatures.

    The WPL 19/24 – for indoors and outdoors

    The WPC 04/05/07/10/13

    The compact brine water heat pump WPC for indoor installation with integral DHW cylinder can be used in mono mode to provide heating and warm water. These heat pumps are ideal for new builds and modernization projects. The heat pump unit is equipped with a scroll compressor with a soft starter and optimized heat exchangers for improved efficiency. Moreover, the WPC heat pumps ensure an easy and space-saving installation due to the high level of integrated components as well as an extremely quiet operation thanks to multiple anti-vibration coupling.

    The WPW 10 Trend – convenient and robust

    In our academy in Holzminden, we teach about innovative building technology: the way heat pumps work is our theme for today – simple and easy to understand! Click now.

    Where does a heat pump draw its energy from?


    Heat pump with air as heat source

    Heat source: air

    Air heated by the sun is universally available. Air is at its coldest when the most heating energy is needed, such as in winter. However, heat pumps can still extract enough energy for heating at outdoor air temperatures as low as -20 °C. Air-water heat pumps offer the particular advantage of being easy to install, as no extensive ground work or well drilling is required, as in the case of brine heat pumps, for example.

    All air-water heat pumps
    Heat pump with groundwater as heat source

    Heat source: water

    Groundwater stores solar energy very well. Even on the coldest days in winter, temperatures of +7 °C to +12 °C are maintained. The steady temperature level of this heat source enables the heat pump to achieve an almost constant coefficient of performance all year round. Although groundwater of suitable quality is not universally available in sufficient quantities, it is worthwhile using groundwater when possible. Utilising this heat source requires the drilling of a delivery well and a return well. In Germany, the use of groundwater usually requires the approval of the relevant authority: generally the local water board. Your local water board will advise you about the possibility of utilising these waterways.

    All water-water heat pumps
    Heat pump with a geothermal collector as a heat source

    Heat source: ground with a geothermal collector

    Below a depth of approx. 1.20 m to 1.50 m, the ground remains sufficiently warm in Central Europe to allow economical heat pump operation even on cold winter days. For a geothermal collector, the pipe system that absorbs the geothermal heat requires a sufficiently large area of land. It must be about two to three times the area to be heated. In dry, sandy soil, a geothermal collector can extract between 10 and 15 W/m² and up to 40 W/m² in ground that carries groundwater. Geothermal collectors contains an environmentally friendly brine mixture that cannot freeze and which transports the yielded energy to the heat pump evaporator through the pipes. If your property is large enough, you have an inexhaustible reserve of energy and ideal conditions for a brine-water heat pump.

    All brine-water heat pumps

    From modernisation of an older building to a new build: the right heat pumps for your home

    Air-water heat pumps basically differ in terms of where they are installed – indoor air heat pumps inside the building and outdoor heat pumps outside. Outdoor installation is usually the cheaper solution. This is particularly popular in new builds. In highly built-up residential areas where space is at a premium, indoor installation has a clear advantage due to the low external sound emissions. Furthermore, no space is needed outside of the building. This means the look of the building is not affected either – ideal for listed buildings, for example.

    Brine-water heat pumps and water-water heat pumps are always installed indoors.

    The new WPL 19/24 as an indoor installation: the new inverter heat pump from STIEBEL ELTRON for modernisation projects.

    What is the difference between the heat pumps for indoor installation and those for outdoor installation?

    Air-water heat pumps basically differ in terms of where they are installed – indoor air heat pumps inside the building and outdoor heat pumps outside. Outdoor installation is usually the cheaper solution. This is particularly popular in new builds. In highly built-up residential areas where space is at a premium, indoor installation has a clear advantage due to the low external sound emissions. Furthermore, no space is needed outside of the building. This means the look of the building is not affected either – ideal for listed buildings, for example.

    Brine-water heat pumps and water-water heat pumps are always installed indoors.

    Heat pumps for new build

    • Superior efficiency
    • Automatic ventilation recommended
    • Compact units an option

    From energy-plus and passive houses through to low energy houses – those who build a new house today should look to play in the premier energy league. A highly efficient heat pump is practically a given for this. Complete systems with integral ventilation offer outstanding convenience, but a separate ventilation unit or heat pump can also make sense.

    Savings potential when modernising older buildings

    When you opt for environmentally friendly and sustainable energy technology, you contribute to the responsible use of natural resources. There is also a lot of potential for savings when modernising older buildings. Independence from finite resources is increasingly important here as well. After all, independence means freedom. This is exactly what you achieve in energy terms with modern heat pumps. Invest once during your modernisation project to enjoy long-term benefits. Your personal energy transition also adds value to your property, with the side-effect of conserving fossil fuels.  

    Heat pump design during a building project

    The idea of installing a heat pump in your new build has taken hold? Or modernising an older building is becoming more and more important? Avail yourself of our heat pump quotation service*! Simply specify the requirements of the heat pump and get the right products and a non-binding quotation from a qualified contractor in your area in just a few clicks.

    Steps to the right heat pump

    1. Building inspection
    2. Calculate the heat load
    3. Select the heat pump functions
    4. Identify the type of heat pump
    5. Find an installation location
    6. Obtain your personal quotation
    7. Service and promise of guarantee

    Are you interested in modernising an older building? In our "Information & engineering" area we have information on how you can save. We show you sample applications from "affordable" and "convenient" through to "efficient". Find out all about modernising with heat pumps. Understand the process involved in selecting and designing the right heat pump by reading our "Expert tips from a qualified contractor".

    You will find answers to other questions that regularly pop up in our Heat pump FAQ.

    Subsidies for your heat pump

    Once you have decided to opt for a heat pump, you should also look into the available subsidies. One potential option is the subsidy for a "KfW Efficiency House 40 Plus" – the highest subsidy for energy efficient buildings. Our product solutions, which have been tested in the market, fully futureproof your new build. A House of the Future in fact.

    KfW subsidy

    Are you building your own home? Then don't miss out on the possible KfW Efficiency House subsidy. Check out our video entitled "KfW subsidies for a KfW Efficiency House 40 Plus".

    STIEBEL ELTRON offers special solutions for the KfW Efficiency House 40 Plus.

    Market incentive scheme (MAP) and Energy Efficiency Incentive Programme (APEE)

    Energy transition in the boiler room: the German Federal Government revised its market incentive programme for renewables (MAP) in 2015. The Energy Efficiency Incentive Programme (APEE) has also been in place since 1 January 2016. We explain how these work: "Subsidies for Building and Modernisation Projects".

    Field report: House of the Future

    Meinolf Bonnekoh (48) has been an electrician for 15 years. A qualified contractor, he can be found working hard in boiler rooms, day after day. His job mainly takes him in and around city of Soest. For his own apartment building, he decided the building services should be exemplary in terms of energy use. Consequently, he opted for the combination of a STIEBEL ELTRON air source heat pump, controlled mechanical ventilation and a photovoltaic system. In the STIEBEL ELTRON Energy Life blog, Meinolf Bonnekoh shares his experiences with us.

    Seal and awards

    With its innovations, STIEBEL ELTRON is a pioneer in the use of the latest technologies. Our product range includes products certified for new passive house builds that satisfy all requirements in the area of renewables. Take our LWZ 504 integral inverter unit, for example.

    Our products also carry the "ErP" energy label, which rates each product's energy efficiency.

    The independent EHPA quality label also confirms our excellent product quality. The European Heat Pump Association (EHPA) represents the interests of the European heat pump industry. Its aim is to further promote heat pump technology in the European market for residential, commercial and industrial applications.

    STIEBEL ELTRON is also committed to working with associations both at home and abroad. This includes the Bundesindustrieverband Deutschland Haus-, Energie- und Umwelttechnik e.V. [German association for the building services, energy and environment industry – BDH] and the Bundesverband Erneuerbare Energie e.V. [German Renewable Energy Federation – BEE]. Find out more about our activities.

    Energy Label for heating heat pumps

    The top of the "ErP" label displays the name of the manufacturer (I) and the model designation (II) of the product. The rating system categorises heating heat pumps into nine efficiency classes. A++ is the highest energy efficiency class. G denotes appliances with extremely poor values.


    STIEBEL ELTRON products are almost exclusively in the top efficiency class, with all STIEBEL ELTRON heating heat pumps already being in the top category, i.e. classes A to A++.

    More information on the "ErP" label can be found in our FAQ.


    Products from STIEBEL ELTRON are recipients of internationally recognised awards for their outstanding design, such as the Red Dot Award and iF Design Award. The design work and R&D for all of our products is carried out in Germany to ensure "Made in Germany" quality. The STIEBEL ELTRON Group's largest production facility is located in Holzminden, Lower Saxony. We manufacture in various locations around the world for different markets. In doing so, we can draw on more than 40 years’ of experience in the development and production of heat pumps.

    DHW heating with heat pumps

    You need an affordable solution for your domestic hot water: for DHW heating from renewable sources, the DHW heat pump offers a quick and convenient solution. DHW heat pumps are affordable to buy and easy to install. They are outstandingly efficient, as the heat is recovered from the ambient air at the installation site.

    FAQ – answers to frequently asked questions on heat pumps

    * Certain parameters are assumed when issuing quotations. Your qualified contractor will have to confirm and evaluate these in person during an on-site visit. If an alternative solution needs to be found due to the installation location or other factors, the quotation may need to be amended.