Air conditioners can use both heat pumps and resistors for heating, depending on the type of system.
Heat Pumps: Many modern air conditioners are equipped with a heat pump feature, which allows them to provide both cooling and heating functions. A heat pump works by transferring heat from one location to another using refrigerant. During the cooling mode, the heat pump removes heat from the indoor space and releases it outside. In the heating mode, the process is reversed, and the heat pump extracts heat from the outside air (even in colder temperatures) and transfers it indoors. Heat pumps are more energy-efficient than resistive heating systems, as they move heat rather than generating it.
Resistive Heating: Some air conditioning systems, particularly older models or specific types of units, may use resistive heating elements to provide heat. These systems work similarly to an electric space heater, where electrical resistance is used to generate heat. The air conditioner's fan blows air over these heating elements, which warms up and is then distributed into the room. However, resistive heating is less energy-efficient compared to heat pumps because it directly converts electrical energy into heat without any heat transfer process.
It's worth noting that air conditioners with heat pump functionality are generally more versatile and energy-efficient since they can both cool and heat the space. If you're considering a new air conditioner, it's recommended to look for models that offer heat pump capabilities for efficient year-round heating and cooling.