What happens to the heat pump's efficiency as outdoor temperatures drop for air-source models?

As outdoor temperatures drop, the efficiency of air-source heat pumps typically decreases. This phenomenon occurs because heat pumps operate by extracting heat from the outside air and transferring it indoors. As the temperature outside declines, the amount of thermal energy available in the air diminishes, making it harder for the system to extract sufficient heat. Consequently, the heat pump must work harder and consume more energy to provide the same level of heating, which leads to a reduction in its overall efficiency.

In particularly low outdoor temperatures, the situation can become more pronounced. The unit may struggle to provide adequate heating, and auxiliary heat sources may be required to maintain indoor comfort. This reliance on additional heating further diminishes the heat pump's efficiency, highlighting the impact that external temperatures have on its performance. Understanding this behavior is crucial for choosing the right heating solution, especially in colder climates where air-source heat pumps may be less effective.