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Harmful to the environment and still mandatory? Debunking heat pump myths

Some are sceptical about their merits, while others see them as the key to a successful energy transition: we’’re talking about heat pumps, currently the subject of more myths than any other heating system. They don’’t pay off, is the claim, they constantly break down and will even be forced on households under new heating legislation. Then there’’s the high heating costs, the climate-damaging emissions and the mountain of hazardous waste that will result if owners are required to tear out the once-praised technology again in a few years’’ time. These are just some of the misconceptions and fears about this heating solution. But what’’s the real story? Which information is false and what are the actual facts? We explain all in the following sections.  

Good for the climate or difficult to dispose of?

““Soon we’’ll be ripping out all the heat pumps again!”” This off-putting message has been internalised by many people, convincing them of the supposedly climate-damaging impact of this modern heating solution. In practice, however, the picture is different: as the following sections make clear, grey energy is dramatically reduced with climate-friendly refrigerants, there is no need for special disposal task forces and components can usually be easily replaced when necessary.  

The term ““grey energy”” describes the energy consumption associated with a product over the course of its life –– from its production and use to disposal. Critics posit that modern heat pumps perform particularly badly here due to their numerous components and the refrigerants.  

The first point applies equally to all central heating systems: regardless of whether a heat pump or gas heating system is used to generate heat, pipes, pumps and heating surfaces are always needed to distribute thermal energy and transfer it to rooms.  

Refrigerants are indeed a point of criticism –– especially previously widely used fluorinated hydrocarbons (F-gases) such as R-410A, which is 2088 times more harmful to the climate than the same amount of CO2. However, this only applies if it is released into the atmosphere. As heat pumps are closed systems, this does not happen if they are disposed of properly. It is also important to note that the so-called F-gas Regulation is successively banning harmful refrigerants and that subsidy requirements in relation to the use of natural refrigerants promise better conditions.  

Heat pumps work on the basis of a technical process that does not use any combustion. They require only environmental energy and electricity and therefore emit no greenhouse gases or pollutants themselves. Green electricity can be used for carbon-neutral heat pump operation. Heat pumps do not harm the environment –– indeed, the opposite is true. This is also due to the fact that, as a rule, only one kilowatt hour of electrical energy is required to generate three or more kilowatt hours of heat. Other electric heating systems operate with an efficiency of ““just”” 100  percent, supplying around one kilowatt hour of heat for every kilowatt hour of electricity.

Heat pump systems are not silent. This is particularly true of air source heat pumps, which use a fan to draw in outdoor air from which the heat is extracted. However, the noise is barely audible with modern systems such as the Vitocal  250-A from Viessmann. These generate a noise level of just 35  dB(A) at a distance of four metres, which is comparable to a quiet whisper. Optimally set up and adjusted, there are no disturbing effects.  

Today, most materials can be correctly disposed of or even recycled. This applies to the plastics used as well as the metallic materials and electrical components. The same holds for many refrigerants, which can often be reprocessed or recycled. If this is not possible, they are professionally destroyed and converted into thermal energy.  

This statement is partly true. Previous generations of heat pumps, air conditioning systems and refrigerators often used refrigerants with a high GWP (global warming potential), the factor by which a substance is more harmful than the same amount of CO2. However, modern systems use natural refrigerants such as propane (R-290). This has a GWP of three and is therefore far kinder to the environment than R-410A, which was frequently used in the past and has a GWP value of over 2000. In addition to the F-gas Regulation, heat pump subsidies that favour natural refrigerants or will require their use from 2028 onwards are driving a gradual changeover.  

This statement is also partly true. Propane (a natural refrigerant with the R number R-290), for example, is a flammable substance that creates an explosive atmosphere when combined with atmospheric oxygen. However, refrigeration circuits are closed and in any case are filled with very small quantities of refrigerant. The  Viessmann Vitocal  250-A, for example, contains only 1.2  kilograms of propane. This is significantly less than a typical 11  kg gas cylinder for barbecues and poses virtually no danger.

In principle, drilling for wells and probes has the potential to cause damage. But in practice that is very unlikely. A detailed approval process has to be completed before any construction equipment arrives. Specialised companies are only given the go-ahead when the relevant authorities have examined the respective project and declared it safe. Companies must have DVGW certification for measures eligible for subsidies and are required to carry no-fault insurance.

If heating systems overload the power grid, could homes be left cold?

Heat pump heating systems require not only environmental energy but also electricity from the public grid to supply homes with heat. Critics claim that this will put an immense strain on the electrical infrastructure and also lead to blackouts. As a result, they say, suppliers will turn off power to heat pumps first, leaving homes cold during power shortages. Our answers to the following myths show that the situation is different in practice and, as intelligent consumers, modern heat generators are actually beneficial for the energy transition.

That is not true. Everyone who applies for a house connection must specify the required electrical power. The same applies when retrofitting heat pumps if they exceed a certain output limit. Grid operators use the information to check their own capacities before agreeing to the connection. Blackouts caused by the installation of heat pumps alone are therefore virtually impossible. But when it comes to the expansion of renewable energies, German energy infrastructure really does need some improvements. Energy storage and digitalisation are particularly important topics in this regard.

Heat pumps are intelligent electricity consumers that can be controlled very flexibly. This allows them to convert electrical energy into heat in the event of an oversupply of electricity and store it decentrally in the home, perhaps in water storage tanks or directly in the building structure –– for example with underfloor heating. If there is a power shortage due to high loads or low energy supplies, suppliers can temporarily switch off heat pumps. In order to bridge the ““blocking times””, control systems ensure that storage units are filled to capacity beforehand so that homes are not left cold. Connected households often receive more favourable electricity tariffs and the high level of flexibility is of great benefit for our power grids.

This is true and applies equally to all heating solutions. Without electricity, neither control units, burners nor pumps can work. The only exceptions are wood burning stoves, pellet stoves that don’’t need electricity and heating systems with an emergency power supply via a generator or photovoltaic system.

Is it only worth installing a heat pump after extensive modernisation work?

The many myths surrounding heat pumps and their effects on the environment and the grid also extend to their application areas. For example, it is claimed that installing the technology in older buildings is a fairly pointless exercise without a costly complete refurbishment. There is also the preconception that the output is too low for apartment buildings and the technology is unsuitable for single-storey heating systems as well. Our response to the following myths shows that the range of applications for heat pumps is actually quite wide.

For a heat pump to be worthwhile, it must provide a lot of heating energy with a small amount of electricity. The heat source and heating system temperatures must be close to each other for this. The heat source temperature depends on the type of heat pump (air, ground or water) and can only be influenced to a limited extent. However, the temperature in the heating system –– the flow temperature –– depends not only on the insulation standard but also and especially on the heating surfaces. The larger these are, the more heat reaches the home at low heating water temperatures –– one reason why underfloor heating systems provide favourable conditions. In many older buildings, however, a heat pump can operate efficiently when just a few radiators are replaced. This is often a quick job and significantly cheaper than a costly complete renovation.  

This is not the reality. While it’’s true to say that this heating system is not suitable in every case, heat pumps can be operated efficiently in some older buildings. As explained in the previous section, a few new radiators are often all that is needed to create the right conditions. A heating engineer or energy consultant can check whether this is an option in a specific case.  

This is another myth that has been disproved time and again in practice. For example, an apartment building can be heated with a large heat pump or a cascade system. For a cascade, several heat pumps are linked together to supply a building with heat. An intelligent control system switches the various heat generators on or off depending on how much heat is required at any time.

When it comes to complying with GEG requirements, individually heated apartments present owners with major challenges. These can be overcome by, for example, installing a central heating system or decentralised air/air heat pumps. The latter are split air conditioning systems for heating the air. They can be set up, commissioned and operated efficiently without any major conversion work. Another advantage is that air/air heat pumps react very quickly and precisely to changes in temperature requirements. This means they can be operated as needed and are particularly economical.

Are heat pumps really only suitable for a few buildings?

How do heat pumps work and what conditions need to be created to ensure efficient operation? Answers to these questions will help you to debunk the biggest myths for yourself. However, there are also some misunderstandings and false claims regarding how the technology functions. Read the following sections to find out how much is actually true.

This is a myth, because this modern heating system can reliably achieve high flow temperatures. Take high-temperature heat pumps, for example, which compress the refrigerant more than usual. They bring the flow temperature to over 70  degrees Celsius and are suitable for older buildings that have undergone little renovation as well as commercial premises. Whether the technology is worthwhile in a specific instance depends on numerous factors, which can be clarified during an individual consultation.

As larger heating surfaces transfer more heat to rooms, there is a benefit to having an area heating system in place, such as underfloor heating. However, this is by no means the only solution. Large radiators also achieve good results in practice. Even better are special heat pump-compatible radiators that are equipped with small fans to ensure a high output at low flow temperatures as well.  

This myth is often heard in relation to how air source heat pumps work, as they utilise energy from the air for heating. The power demand increases when it is very cold outside, and critics surmise that the output may not be sufficient. However, this is not the case with individually designed heating systems. These have sufficient reserves to maintain a comfortable temperature in the home on very cold days.  

This does not apply to all heat pump heating systems. Although system efficiency may decrease as the outside temperature falls, coefficients of performance of three or thereabouts can still be achieved even at temperatures around freezing point. This means that the heat pump provides around three kilowatt hours of heating energy with one kilowatt hour of electricity. Please refer to the datasheet for the respective heating system to get the coefficient of performance under different conditions.

It is quite normal for air source heat pumps to ice up regularly. This is because of the refrigerant, which absorbs heat from the outdoor air at the evaporator. If the temperature there falls below the air dew point, water condenses. Fine droplets collect on the evaporator or outdoor unit and freeze at low temperatures. Modern heat pumps have various strategies for this. They defrost the ice at regular intervals and ensure that the overall output is maintained.

Are heat pumps a new technology that is still far from reliable?

Service life plays a decisive role in the cost-effectiveness of a heating system. However, there are numerous myths specific to this, including suggestions that heat pumps are new, untested and will not even last ten years. Our responses to the following claims show that this is not true.

Heat pumps work just like refrigerators and air conditioners. They are made up of the same components and have been in practical use for many years. Viessmann even launched the first heating system of this type back in 1978. This debunks the claim that the technology is new and unexplored.

Heat pump efficiency depends on many factors –– not only the temperature conditions, but also the characteristics of the heating system and user habits. It is therefore not possible to provide universally valid values. However, various details in the datasheets for the heating appliances help to provide a realistic picture. These include coefficients of performance (COP) at different temperatures and seasonal coefficients of performance (SCOP) for varying climatic conditions. The latter describe the average coefficient of performance over a year and are comparable to the  seasonal performance factor. As local conditions vary greatly, only standardised values can be determined. These can be used as the basis for individual consultations to establish whether the technology is worthwhile in a specific case.

Just like other heat generators, heat pumps have an average service life of over 15  years. In cost-effectiveness analysis, the calculated service life is even 20 years (VDI  2067). This corresponds to the theoretical service life of a gas condensing boiler and is even longer than that of gas burners with fans and accessories (12  years according to VDI  2067). Components that fail over this period can generally be repaired or replaced. This applies to the heat exchangers as well as to the compressor and the system’’s electronic components.

Are heat pumps actually required by law?

It is claimed that the new heating law is really a heat pump law that allows almost no other solutions –– this has been a frequent refrain since the amendment to the German Buildings Energy Act (GEG 2024) was announced. However, even a cursory reading of the text of the act makes clear that this is not entirely true, as we explain here.

This is simply not what the German Buildings Energy Act (GEG) states. Other heating systems that run on renewable energies will also be permitted from 2024. These include biomass heating systems, solar thermal systems and special fuel cell heating appliances. Consumers will even be allowed to install new oil and gas heating systems until municipal heat planning has been finalised. However, these must then be gradually converted to renewable energies. The situation is similar if a hydrogen or district heating network is planned in your region. For hydrogen, government will permit the installation of H2-ready gas condensing boilers (and subsidise them proportionately). If the home is connected to a heating network in the future, any heating system can be considered for a transitional period.

An energy performance certificate shows the level of energy demand or consumption for a building. Its purpose is to inform tenants, buyers and owners about the energy condition of the building and nothing more. Having a heat pump installed may result in a better energy performance certificate rating, but is not a requirement to obtaining this document.

That is a myth. However, fines may be imposed if GEG obligations are not met. One example is the requirement to replace standard oil and gas boilers after 30  years. If you heat your home using low temperature or condensing technology, you don’’t have to replace your heating system. The same applies to owners of detached and two-family houses already living in their property before 1 February 2002.

This is a misleading and unsubstantiated claim. The government is not planning such an approach. Moreover, it’’s not plausible, as heat pumps with a coefficient of performance of around 3 or more draw less electricity from the grid than other electric heating systems. As intelligent and easily controllable consumers, heat pumps actually benefit the grid and the expansion of renewable energies. This is not the case with direct electric heating systems.

Does a heat pump increase heating costs?

Too expensive to buy, costly to operate and uneconomical: these are further heat pump myths that are repeated time and again. The degree of truth behind them depends on the individual case. An optimally designed and adjusted heat pump delivers sustainable cost savings. This is already the case today and will become even more so if the price of electricity from renewable energies falls, as the following sections show.

Without knowing the building and the local conditions, it is not possible to make a statement about the electricity and heating costs as they depend on numerous individual factors. If the conditions are favourable, the heating system will operate with a high seasonal performance factor. It will require little electricity to provide sufficient heat and reduce heating costs on a sustainable basis.

The trend towards flexibilisation on the electricity market will also contribute to this. Suppliers will sell electricity at fluctuating prices in future. Any excess electrical energy produced will be particularly cheap. In future, heat pumps will be able to use this to build up a heat reserve and draw less electricity from the grid at times when it is more expensive. Other heating systems will not be able to do this.  

There are various reasons why homeowners are currently more reluctant to buy heat pumps. For one, the new heating law is causing great uncertainty. For another, the expected subsidies have a part to play. While the government will subsidise the installation of a heat pump by up to 40  percent in 2023, this will rise to up to 70  percent in 2024 and there will be favourable supplementary loans. The prerequisite is that no supply or service contracts have been awarded at the time of application.

However, please note that this will temporarily change due to an exception in the recently adopted subsidy directive. According to this, anyone who replaces their heating system from the date the directive was published in the Federal Gazette (including in 2023) will have until 30 November 2024 to apply retroactively for the better subsidy announced for 2024. (This does not apply to the construction, conversion or extension of a building distribution system.)

As with heating costs, it is not possible to make a sweeping statement in this regard. Although costs are comparatively high at the moment, this is due to numerous factors. Take, for instance, planned peripheral measures. Owners who retrofit underfloor heating throughout their home will incur higher expenses. The good news is that the government already subsidises all costs associated with replacing heating systems. While subsidies of 25 to 40  percent are currently available, renovators will receive a subsidy of up to 70  percent for a new heat pump from 2024. There will also be the option of taking out a favourable supplementary loan.

It’’s important to note that you have to consider more than just the purchase costs to determine whether it’’s worth investing in a new heating system. Consumption costs are another major factor. Experts can assess these on an individual basis and make a reliable statement on the cost-effectiveness of the proposed heating system.  

That is not true. With a new, individually designed and correctly set heat pump, you can heat your home efficiently. No carbon or other emissions are released and the value of the property generally increases. The effect is particularly large if the entire heating system is modernised (for example with underfloor heating) and a  photovoltaic system  partially covers the electricity demand itself.

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