How do air-source heat pumps function in extremely cold temperatures?

Air-source heat pumps function by transferring heat from the outside air to the inside of a building. In extremely cold temperatures, the amount of available heat in the outside air decreases significantly, which affects the heat pump's operational efficiency.

As the temperature drops, the heat pump must work harder to extract heat from the cold air, leading to a reduction in efficiency. This is because the heat transfer process becomes less effective, resulting in a lower coefficient of performance (COP). The colder the external air, the more energy the heat pump uses to provide the same amount of heating, which can also lead to higher energy costs and reduced heating capacity.

In contrast, while some systems may switch to auxiliary heat sources or operate differently under extreme conditions, they do not function as regular heaters in the conventional sense; they still rely on the principles of heat transfer. Therefore, the understanding that their efficiency decreases in extremely cold temperatures highlights the specific challenges air-source heat pumps face in maintaining effective heating performance.