Germany’s ruling coalition plans to slow parts of its renewables push and amend a key heating law amid fossil-fuel industry lobbying and public hesitation over alternatives like heat pumps. Though new buildings frequently feature heat pumps, many Germans remain skeptical of the technology as an alternative to heating systems that rely on gas, oil or coal.
Yet heat pumps have long been standard in countries like Norway and Finland, where winter temperatures often drop below −20 °C (−4 °F) for weeks.
How effective are heat pumps in extreme cold?
Subzero temperatures are not a fundamental problem for heat pumps. The refrigerants used in the heat exchanger have extremely low boiling points — below −40 °C — so even when it’s very cold a heat pump can absorb ambient heat from outside air and use it to warm a building. Air‑source heat pumps in use across Scandinavia or in the Arctic work well at temperatures as low as −25 °C. When it’s colder, they can be supplemented by an electric heating element to give the system an extra boost.
Ground‑source heat pumps, which extract heat from soil or groundwater, are even more efficient. Soil and groundwater temperatures stay relatively stable and are generally warmer than winter air. These systems can tap heat from as deep as 300 meters, where temperatures remain around 10 °C even if it’s −50 °C at the surface.
Efficiency in cold weather: slightly reduced but still superior to gas
Heat pumps draw on ambient warmth, so most of the energy they deliver is already present in the environment rather than produced by burning fossil fuels. In Scandinavia, heat pumps typically get about two‑thirds of their energy from the surrounding environment, with the remainder coming from the compressor’s motor. On a yearly average a heat pump can deliver roughly 3 kWh of heat for every 1 kWh of electricity used — an efficiency of about 300%. By comparison, a standard gas heating system is typically under 100% efficient; older models often fall below 80%.
Performance varies with outside temperature. At 12 °C a modern heat pump can transfer up to 10 kWh of warmth for 1 kWh of electricity (COP ≈ 10). As temperatures drop the compressor must work harder and the performance ratio falls. A 2023 study in Joule found that modern heat pumps operating at −20 °C in Finland moved about 2 kWh of heat per 1 kWh of electricity (COP ≈ 2); at −30 °C the ratio was between 1 and 2. Trials in Alaska of a cold‑climate heat pump showed similar results: about 2 kWh per 1 kWh at −25 °C and 1.8 kWh at −35 °C.
Heat pumps standard in Scandinavia
Despite frigid winters, heat pumps are the dominant heating technology in Norway, Sweden and Finland. In Norway, 66% of households use heat pumps; in Finland 55%; and just over half of Swedish homes. For new buildings, more than 90% of installed heating systems in all three countries are heat pumps. Cities with district heating are increasingly deploying very large heat pumps to replace polluting fuels. In Helsinki, the world’s largest air‑source heat pump is expected to start operating by the end of 2026, supplying heat to 30,000 homes, transferring up to 33,000 kW of heat and operating efficiently at temperatures down to −20 °C, avoiding about 26,000 tons of CO2 emissions.
Choosing the right heat pump
Heat pumps and air‑conditioners use the same proven refrigeration technology as refrigerators and can heat or cool most buildings. Many households save on heating bills: in Germany’s relatively mild climate (comparable to the Pacific Northwest or New England), homes with heat pumps already save at least 30% on bills; in Sweden savings exceed 50%. Norway banned heating oil in 2020 to reduce greenhouse gas emissions.
Before installing a heat pump, consult an expert. Better insulation improves efficiency, and specialists can recommend the best system for your location. Air‑source units are often less expensive upfront than ground‑source models because they are more widely produced and don’t require costly drilling.
This article was originally written in German.