Too expensive and too cold?
Myths about the heat pump in a fact check
May 21, 2023, 8:09 p.m
To protect the climate, the federal government is saying goodbye to gas and oil heating. In the future, the heat pump will also ensure warm apartments and houses. The skepticism about the technology is expressed in various claims – for example that it doesn’t pay off, that it is harmful to the climate and, above all, that it doesn’t work in old buildings. This fact check clarifies what is true and what is not.
Claim: With a heat pump, the radiators do not get really warm.
Evaluation: Incorrect.
Facts: The radiators get warm, but not scorching hot. “Therein lies the savings potential,” says department head Arian Freytag from the consumer center in Mecklenburg-Western Pomerania. Heat pumps are low-temperature heating systems, explains Katja Weinhold from the German Heat Pump Association (BWP). With technology, heat is extracted from the environment (air, water, earth) and brought to a higher temperature, usually between 35 and 55 degrees Celsius, with the help of electricity. With this so-called flow temperature, the heating water flows through the system to the radiators.
According to Weinhold, high-temperature heat pumps with a flow temperature of up to 75 degrees are less efficient due to higher power consumption and are more expensive overall. “The radiators are definitely warm enough,” says Weinhold. A research project by the Fraunhofer Institute also comes to the conclusion that the heat is sufficient. The scientists examined buildings between 15 and 170 years old with heat pumps. In terms of flow temperatures, the 27 outdoor air heat pumps averaged just under 44 degrees and the eleven ground source heat pumps a little over 45.
However, heat pumps cannot keep up with conventional oil and gas heating systems. During combustion, temperatures of several 100 degrees are sometimes generated, explains Weinhold, “whereby most of this heat evaporates through the chimney”. The temperatures used to be set unnecessarily high on boilers, says Peter Kafke, team leader for energy advice at the Federal Association of Consumer Organizations (VZBV). Radiators got so hot “that you could fry a fried egg on them,” said BWP spokeswoman Weinhold.
Claim: Homeowners have to pay up to 300,000 euros.
Evaluation: Misleading.
Facts: In order to come close to a sum of 300,000 euros, an old house would have to be completely renovated in terms of energy. Peter Kafke from the VZBV illustrates: If not only too small radiators are replaced by larger ones, but a new underfloor heating system is installed, that drives up the costs. According to him, this includes new screed and floor coverings throughout the house. If you then insulate the house and install new windows, you could reach 200,000 euros. Kafke calls this “the great exception”. With the amount of 300,000 euros, Katja Weinhold thinks of a house with several parties, which is also in need of renovation. According to the BWP spokeswoman, this has nothing to do with simply installing a heat pump.
An example: In a single-family house with 150 square meters of living space, the oil or gas heating is to be replaced with a heat pump. Weinhold puts the average costs for this at 25,000 to 65,000 euros. The financial range arises from the type of heat generation (air, water, earth), the performance of the heat pump and the necessary environmental measures. According to the information, the installation should be included.
Claim: A heat pump does not pay off financially in the long term.
Evaluation: Often wrong.
Facts: The initial investment for a heat pump is higher than for oil or gas heating, says Katja Weinhold from the BWP – despite state subsidies (maximum 40 percent, capped at 60,000 euros per residential unit). Additional measures such as radiator replacement or insulation make it more expensive. This means that the expenses for the new heating system have to be recouped over the years. Even without the expected reduction in the price of heat pumps, the system will pay for itself after 25 years at the latest, according to the BWP spokeswoman.
A calculation by the Fraunhofer Institute shows: A partially renovated single-family house with an area of 150 square meters to be heated is operated with an average efficient heat pump, which generates three kilowatts of heat from one kilowatt of electricity (annual performance factor 3 – JAZ 3). Compared to gas heating, you save more than 150 euros per month. A gas price of 25 cents and an electricity price of 35 cents per kilowatt hour (kWh) were used as a basis. This means that although the heat pump requires more expensive electricity to operate, it requires fewer kilowatt hours than gas heating, depending on its efficiency. This is also the basis of the comparison made by VZBV team leader Peter Kafke.
Example of gas heating: He calculates that a house needs 20,000 kWh of heat per year, so 300,000 kWh in 15 years. At a gas price of 20 cents per kWh, that’s 60,000 euros for operation. In addition, there are about 10,000 euros for the heating system. That makes a total of 70,000 euros.
Example heat pump: This needs the 20,000 kWh divided by the JAZ. With a good heat pump (JAZ 4) that would be 5,000 kWh of electricity per year – at 40 cents per kWh, that is 30,000 euros in 15 years. If the heat pump costs 30,000 euros and a third is subsidised, the total is 50,000 euros. According to Kafke, this means savings of 20,000 euros compared to gas heating. The situation would be different with an exceptionally poor heat pump (JAZ 2): It requires 10,000 kWh of electricity for 20,000 kWh of heat. At 40 cents per kWh, that would be 60,000 euros in 15 years, as with gas, and ultimately a loss due to the more expensive system.
Claim: A heat pump is no more climate-friendly than a gas heater.
Evaluation: Incorrect.
Facts: Gas heating cannot keep up with a heat pump. According to the Federal Environment Agency (UBA), anyone who uses a gas heater generates around 218 grams of environmentally harmful carbon dioxide (CO2) per kWh. That means: For a single-family house with 20,000 kWh, that’s around 4.4 tons of CO2 per year.
The heat pump, on the other hand, needs electricity to operate. “Depending on the production, this can be clean or harmful to the climate,” explains Arian Freytag from the consumer center. According to UBA, the electricity mix in Germany (2022: 46.2 percent from renewable energies) produces 434 grams of CO2 per kWh. A mediocre heat pump with JAZ 3 requires a third of the 20,000 kWh of heat to be generated as electricity. This results in around 145 grams of CO2 emissions per kWh of heat. Calculated over the year, that is almost 2.9 tons of CO2. Compared to natural gas, this means savings of around 35 percent.
If you want to further relieve the burden on the environment, you have two options with the heat pump. If you buy a more powerful heat pump (JAZ 4), based on the current electricity mix, around 2.2 tons of CO2 will still be produced per year. “A good heat pump halves the CO2 emissions compared to gas heating,” says VZBV team leader Peter Kafke. If you only get your electricity from renewable energies, you can significantly reduce CO2 emissions again. “With a 100 percent green electricity tariff, the heat pump is far more climate-friendly than gas heating,” explains Freytag.
Claim: In old buildings, the installation of a heat pump is also impossible because of the lack of underfloor heating.
Evaluation: Incorrect.
Facts: “It doesn’t matter whether you have underfloor heating or radiators,” says Peter Kafke from the VZBV. The flow temperature must be right. According to the team leader from the consumer center, these can often be sufficient even in old buildings with radiators that have not been renovated much. The radiators already installed are often oversized and therefore suitable for heating with heat pumps, adds department manager Freytag. If anything is unclear, Kafke advises an examination. This could lead to a “replacement of individual radiators and individual insulation measures” that ensure that it gets sufficiently warm with a low flow temperature.
The fact that heat pumps only work with underfloor heating is a persistent myth, says BWP spokeswoman Weinhold. “The heat pump loves large heating surfaces, but doesn’t necessarily need them.”