How does an air-source heat pump function differently from a ground-source heat pump?

An air-source heat pump functions by extracting heat from the air outside a building, even when temperatures are relatively low. This process involves the use of refrigerant, which absorbs heat from the outdoor air and then compresses it to a higher temperature before transferring it indoors to provide heating. The efficiency of an air-source heat pump can often still be significant in colder climates, thanks to advancements in technology that allow them to operate effectively at lower outdoor temperatures.

In contrast, a ground-source heat pump, or geothermal heat pump, extracts heat from the ground. The ground maintains a more consistent temperature compared to the air, making these systems effective for heating and cooling.

While it is true that many heat pumps rely on electricity to operate, this is a common characteristic and does not specifically distinguish air-source from ground-source heat pumps. The unique aspect that sets air-source heat pumps apart is their reliance on ambient air for heat extraction.

Therefore, focusing on the method of heat extraction from the air justifies the choice of the correct answer.