How a heat pump heating system works
Heat pumps have probably become the most discussed and controversial component of the energy transition – in private households as well as in businesses and industry. At Envision Solutions, we are always keen to share our knowledge of physical principles, and today we answer the question: How does a heat pump manage to generate usable heating energy from environmental energy, and why is it considered particularly energy-efficient and climate-friendly?
In this article, we explain how a heat pump works, what physical principle it uses, and where we have been using them in our everyday lives for years. You will also learn about the different types of heat pumps available, how efficient they are, and why they are an important step towards sustainable energy supply for businesses.
How does a heat pump work in principle?
A heat pump is basically a system that removes energy from one system and transfers it to another. That may sound very abstract at first, but it can be easily understood as follows: if I extract energy from a system, it becomes colder; if I add energy to it, it becomes warmer.
A refrigerator, a freezer, and even the air conditioning in your car or office all work on the same principle, except that here the heat is pumped in the other direction.
The basic physical principle behind this process is based on the evaporation and condensation process of a refrigerant. This circulates in a closed circuit, absorbs heat at low temperatures, is compressed, and then releases the absorbed energy at a higher temperature level. This makes the refrigerator cold and the cooling fins behind the appliance warm. The heat pump as a heating system reverses the process and releases the cold into the outside area. In this way, even cold outside air or cool soil can be used to generate enough energy to heat buildings efficiently.
The physical principle behind the heat pump: utilising heat from the environment
Let’s delve a little deeper into the subject. How exactly does it all work? Let’s leave the refrigeration machines aside for now and concentrate on the heat pumps. One of the most important elements for operation is the refrigerant. This is usually a compound of hydrocarbons and occasionally other substances, which are characterised by their very low boiling point. In the past, fluorocarbons were predominantly used for this purpose, but they were banned in order to protect the ozone layer. The refrigerant is cryptically designated with an R and a number, but this often refers to well-known substances such as water (R718), carbon dioxide (R744), or propane (R290). Refrigerants differ in terms of toxicity, efficiency, and global warming potential and will not be discussed in depth in this article. Let’s move on to how they work.
In the first step, the liquid refrigerant absorbs heat from the environment in an evaporator. Due to its low boiling point, it evaporates even at very low temperatures. The gaseous refrigerant is then compressed by a compressor. The increase in pressure also causes its temperature to rise significantly—and the heat that has been “pumped up” in this way can be transferred to the heating system in the condenser.
After the refrigerant has released its heat, it liquefies again, expands in the expansion valve, and cools down. The cycle begins again. In this way, environmental heat is continuously converted into heating energy—a clear example of applied thermodynamics.
The energy used, namely electricity, acts as a kind of intermediary and accounts for only a small proportion of the actual heat consumption. This means that a heat pump can also provide significantly more energy for heating than was used.
The principle demonstrates how physically elegant and energy-efficient heat pumps are: with low power consumption, environmental energy that would otherwise remain unused is made usable.
Types of heat pumps: air, water and ground source heat pumps compared
Heat pumps differ primarily in terms of the medium from which they extract heat. Depending on the location, geological conditions, and energy requirements, air, water, or ground source heat pumps are used. Each of these variants has specific strengths and areas of application – the decisive factor is choosing the right one for the respective application.
Air-to-water heat pumps are the most widely used. They extract energy from the outside air and transfer it to the heating system. Their advantage lies in their simple installation and low investment costs, as no drilling or permits are required. However, their efficiency varies with the outside temperature, which is why they are slightly less efficient in very cold climates. Due to efficiency improvements in recent years, air-to-water heat pumps are gradually replacing other technologies, especially in the private sector.
Brine-water heat pumps (geothermal heat pumps) utilise the heat stored in the ground or groundwater. Geothermal probes or surface collectors are used to obtain energy at a constant temperature, regardless of the season. These systems offer high-efficiency and stable performance but require higher initial investment and professional planning.
Water-water heat pumps, as their name suggests, draw on the thermal energy stored in water. Water-water heat pumps are often used to tap into waste heat sources, for example, when cooling water is produced elsewhere in the production process and can then be used as a source for heat generation.
Other possible applications include rivers and groundwater. The former will be used more frequently in the future in large heat pumps for heating networks.
Water-to-water heat pumps achieve maximum efficiency, particularly when the temperature of the heat source remains constant and due to the comparatively high heat capacity of water.
A direct comparison shows that while air source heat pumps are more flexible in their application, ground source and water source heat pumps offer the highest efficiency potential, albeit with a higher investment and more complex approval procedures.
Efficiency, coefficient of performance (COP) and hot water: How efficient is a heat pump really?
The efficiency of a heat pump is primarily described by its coefficient of performance, also known as COP. This indicates how much heat energy a heat pump generates in relation to the electrical energy consumed. A COP value of 4, for example, means that 4 kWh of usable heat is obtained from 1 kWh of electricity.
In practice, however, the COP value depends on several factors:
- the temperature of the energy source (air, water, ground),
- the desired flow temperature in the heating system,
- and the quality of the plant components and their maintenance.
The smaller the temperature difference between the heat source and the heating system, the more efficiently the heat pump works. That is why low-temperature systems such as underfloor heating are particularly well suited to achieving high efficiency levels. And why it also makes sense to separate hot water production, which requires consistently higher temperatures, from the heating system.
In addition to COP, the annual performance factor (APF) is also frequently used, which reflects efficiency over an entire year – including seasonal fluctuations. Modern heat pumps achieve APF values between 3 and 5, which means that they deliver three to five times as much heat energy as they consume in electricity.
This makes heat pumps one of the most energy-efficient heating technologies—especially when they are powered by renewable electricity. Not only does this save energy, it also significantly reduces CO₂ emissions. This means that even for industrial high-temperature heat pumps, there will be no alternative to heat pumps in the long term.
Limitations and challenges: heat pumps in winter
As efficient and climate-friendly as heat pumps are, they have technical and economic limitations that must be taken into account during planning and implementation. A heat pump is not a “one-size-fits-all” system, but must be individually tailored to the building, its use and its location in order to function optimally.
A key issue is the temperature difference between the heat source and the heating system. The greater the difference, the more electrical energy the heat pump must use to achieve the desired heating output. In existing buildings with old radiators and high flow temperatures, this can significantly reduce efficiency. In such cases, accompanying measures such as replacing radiators or insulating the building may occasionally be necessary. But here too, there is no need to worry: heat pumps have now been installed in many old buildings and are running, in some cases with excellent seasonal performance factors, without major conversions.
Nevertheless, the investment costs pose a challenge for many businesses and households. Although heat pumps usually pay for themselves after a few years thanks to lower operating costs and government subsidies, the initial purchase costs are higher than for conventional heating systems.
Finally, the power supply also plays a role. The carbon footprint of a heat pump depends crucially on the proportion of renewable energies in the electricity used.
Finally, here is a practical example: many of our customers are currently facing the difficult task of converting their old heating systems to more modern ones. A complete switch to heat pumps is largely uneconomical, as the temperatures required in the buildings are too high and there are often insufficient financial resources available for new construction. Nevertheless, we are still proceeding with installing heat pumps, including air-to-water heat pumps. For about half of the year, these provide efficient heating, even at high flow temperatures, especially when cooling is required elsewhere at the same time. This allows both the advantages of the heat pump and the high temperatures of the existing system to be utilised simultaneously.
Conclusion: Why the future of heating technology is electric
The heat pump symbolises the shift in heating technology: away from fossil fuels and towards electrically powered, highly efficient systems that harness environmental energy. Its physical principle has been known for decades, but it is only through modern technology, improved refrigerants, and the integration of renewable energies that it can reach its full potential.
Today, electrically powered heat pumps offer the possibility of combining heating, cooling and hot water production in a single system – and with significantly lower energy consumption. Especially when combined with photovoltaic systems or green electricity tariffs, their operation becomes virtually climate-neutral. Heat pumps thus make a decisive contribution to the decarbonisation of the building sector and to the achievement of national climate targets.
From an economic perspective, there are also many arguments in favour of making the switch: operating costs are low, the technology is durable, and dependence on fossil fuels is significantly reduced. Although switching to heat pump technology requires an initial investment, this pays off in the long term in the form of energy savings, stable energy costs and a better sustainability balance.
In short, the future of heating is electric. Heat pumps demonstrate how physical principles and modern engineering can work together to reduce energy consumption while promoting climate protection. Investing in this technology today sets the course for an energy-efficient and sustainable future.
This blog article was created with the support of generative AI and then carefully supplemented and corrected by us. In addition, comparable tools were used to perform SEO optimisation (this ensures that search engines find and rank this article highly). For this reason, the following keywords were added to the text, which could not be included in the text without compromising readability: how a heat pump works, condenser, function of a heat pump, air-water heat pump, type of heat pump, operation of a heat pump, fan, heating, heating water, heat distribution and storage system, cost-effective, particularly efficient; In addition, the English version of the article was translated using comparable software but carefully revised by a non-native speaker. Please use the contact form in case of serious linguistic mishaps.