Heat pumps – 7 biggest myths and fact check

23.08.2023

GERMANY: One alternative to climate-friendly heating is heat pumps. Some heat pump homeowners are not convinced or feel that their own home is unsuitable for heat pump applications. The information program Zukunft Altbau, funded by the Ministry of the Environment of Baden-Württemberg, has carefully checked some of these claims and, as a result, the reservations turned out to be incorrect or partially correct, therefore they belong to the realm of myths.

By 2045, Germany should become climate neutral, and some federal states, such as Baden-Württemberg, even in 2040. The buildings sector is responsible for about 30% of greenhouse gas emissions and therefore has an important role to play in climate protection. Heat pumps can make a very big contribution to this: unlike hydronic or gas heating systems, they do not burn fossil fuels, so their potential for reducing CO2 emissions is very high.

In recent years, more and more people in Germany are choosing heat pumps as their heating system. This technology is currently the most common type of heating in new one- and two-family houses, and is also gaining importance in existing small houses. Around 1.3 million heat pumps are currently installed in Germany and 500,000 new systems are expected to be added every year from 2024. The goal is to have 6 million installed heat pumps by 2030. However, many homeowners are still unsure and hesitant, hence it's time to clear up some of the most common heat pump myths.

THE 7 MOST COMMON HEAT PUMP MYTHS

MYTH 1: HEAT PUMPS ARE ONLY SUITABLE FOR NEW OR FULLY RENOVATED BUILDINGS

This statement is not true, but is one of the most enduring legends. Heat pumps are useful not only for new residential buildings, but also for existing homes, even if they have not been completely renovated, notes Frank Hettler from Zukunft Altbau. This has also been shown in field tests by the Fraunhofer-Institute for Solar Energy Systems ISE. Existing proven heat pumps show decent performance even if the buildings have only been partially refurbished.

For heat pumps in existing buildings, individual insulation measures or even just the installation of large radiators are often sufficient. Thus, many old houses can be properly heated with a maximum heating medium temperature of less than 55°C. This is considered a critical limit for the use of a heat pump. Heat pumps can also heat water more, but at higher temperatures they work much less efficiently.

Completely unrenovated houses should always have extensive insulation measures, which makes the operation of the heat pump more expensive. In principle, the better the insulation, the lower the heating costs. By the way, this applies to all heating systems.

MYTH 2: HEAT PUMPS ONLY WORK WITH FLOOR HEATING

It is not true. Thus, heat pumps work most efficiently with surface heating, such as floor, wall or ceiling heating. “Due to the special surface area, underfloor heating is best at dissipating heat into the room,” notes Jörg Knapp of the Baden-Württemberg Association of Plumbing, Heating and Air Conditioning Specialists. "They don't need to heat the water as much as you would with regular radiators."

But heat pumps work great with conventional radiators. However, it is highly advisable to have the heat output of the radiators checked by specialists and, if necessary, to replace individual radiators with larger models. The larger the radiator, the less it needs to heat up in order to heat the room enough. Thus, it is possible to reduce the temperature of the heat carrier, which reduces the heating consumption. Just to use a heat pump effectively, you don't have to destroy the floor in existing homes to implement underfloor heating.

MYTH 3: HEAT PUMPS DO NOT WORK AT LOW TEMPERATURES

This is wrong. "Heat pumps heat the house without problems, even at double-digit sub-zero temperatures," emphasizes Jörg Knapp. "At such temperatures, unsuccessful operation of the system is excluded, even a completely uninsulated house warms up in winter." Only electricity consumption grows in severe frost - less in renovated houses, more in non-repaired ones. Such low temperatures are rare in Germany, even in winter. Today they meet only a few days a year and only a few hours - almost never on the Rhine plain, rather in the mountains and in the east.

Basically, a heat pump also works well in cold climates and is relatively popular there. Looking at a map of Europe, most heat pumps are installed in Scandinavia. And the average and minimum temperatures there are much lower than in Germany. Heat pumps that use the heat from the ground, sewers or another so-called warm heat source are advantageous, especially when the outside temperature is very low. Then they work more efficiently than air-to-water heat pumps. However, these systems usually require higher investment costs.

MYTH 4: HEAT PUMPS ABSORB ELECTRICITY AND LOAD THE LOCAL POWER GRID

This is also not true. With a normal building energy standard, heat pumps generate about 3-4 kWh of heat from the environment using one kWh of electricity. If the factor is three, approximately two-thirds of the heat comes from the environment and one-third from electricity. "A single-family house with a living area of 120 m2 requires only about 4 kW of electricity from the mains for a typical heating output of 12 kW", explains Frank Hettler from Zukunft Altbau. “If you turn on the output of an additional heater, usually integrated in heating systems on a heat pump, you get a maximum of 10 kW. Only during cooking or baking requires the same amount of electricity.” You can also save on electricity by installing your rooftop photovoltaic system.

Myth 5: Heat pump heating is too expensive

Consideration of the overall costs plays a crucial role. True, the cost of buying heat pumps is much higher than, for example, gas heating. On average, the cost of purchasing and installing equipment ranges from €30,000 to €45,000 compared to about €15,000 for a gas condensing boiler. However, the state provides a high level of financial support, up to 40% so far, thus additional investment costs are much lower.

However, the economic efficiency of a heating system depends not only on the purchase price, but above all on the operating costs over a period of operation of at least 20 years. And with well-planned heat pumps, they are usually lower than with gas or liquid heating. According to market researcher Prognos, a kilowatt-hour of gas is likely to cost around 12 cents on average in the medium term. The cost of electricity is expected to be around 30 cents per kWh over the medium term, with heat pump tariffs expected to be reduced.

If a heat pump generates more than 3 kWh of heat using 1 kWh of electricity, this saves money annually. If you have a rooftop PV system and use some of the cheap solar energy for a heat pump, the amount goes up even more – electricity from the solar system only costs about 12-14 cents per kWh. In addition, natural gas will become increasingly expensive in the long run due to rising CO2 prices, making heating with a heat pump increasingly attractive.

Conclusion: in the future, savings in operating costs will in many cases be greater than higher investment costs. Therefore, heating with a heat pump is often the cheaper option. This has already been proven for air source heat pumps, the dominant heat pump technology on the German market: in their 2021 and early 2023 studies, the Fraunhofer-Institute ISE and the Prognos agency concluded that air source heat pumps in new single and multi-family houses are always cheaper than gas . Even in existing buildings, air source heat pumps cost at least the same as gas heaters. If a photovoltaic system is used, they are usually cheaper.

MYTH 6: HEAT PUMPS ARE TOO LOUD

Essentially: geothermal heat pumps and groundwater heat pumps are almost inaudible. The fan generates noise only with air source heat pumps. In recent years, heat pump manufacturers have continued to reduce the operating noise level of their systems. "The sound of many heat pumps now almost disappears into ambient noise," notes Hettler. "It's only in the dead of winter that the heat pump is heard more clearly at full load, but that's when you still have your windows closed and you don't hear any noise."

Legislators have also been prudent and taken appropriate measures: in purely residential areas, the heat pump should not be louder than 50 decibels during the day, while the permitted level is reduced to 35 decibels at night. Currently, there are heat pumps with whisper mode and soundproof housings that do not exceed 30 decibels at full load. For comparison: 30 decibels corresponds to a conversation in a whisper.

MYTH 7: HEAT PUMPS DO NOT CONTRIBUTE TO A BETTER CLIMATE

Of course, this is not the case, since most of the heat comes from the environment in a climate-neutral way. Thanks to the growing share of electricity from renewable sources in the coming years (now about half), heat pumps will become even more climate-friendly in the future. In terms of CO2 emissions, heat pumps show – already with the current share of coal electricity in the energy mix throughout the year – much better results than condensing systems using natural gas or liquid fuels. By connecting a heat pump to a photovoltaic system, CO2 emissions are reduced even further.

CHECK YOURSELF: IS YOUR HOME SUITABLE FOR A HEAT PUMP?

With a simple test, you can find out for yourself whether your own home is suitable enough for a heat pump. It works like this: on a very cold day during a long frost, you set the temperature of the boiler coolant to 50-55°C, and then set the thermostats on the radiators to 20°C, this is position 3 on the thermostat wheel. If all rooms are warm enough, the house is suitable for a heat pump. If not, then energy improvements need to be made. Energy consultants and heating experts will show you the best way to do this.

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