Air conditioning heaters, also known as heat pumps, are versatile systems that provide both cooling and heating capabilities for indoor environments. While air conditioners are commonly associated with keeping us cool during the hot summer months, they can also efficiently heat spaces during colder seasons. In this article, we explore the fascinating technology behind air conditioning heaters and how they work to keep us comfortable year-round.

  1. The Basics of Heat Transfer:

To understand how air conditioning heaters work, it’s essential to grasp the concept of heat transfer. Heat naturally moves from warmer areas to cooler areas until an equilibrium is reached. Air conditioning heaters leverage this principle to extract heat from the outdoor air (even in cold temperatures) and transfer it indoors.

  1. The Refrigeration Cycle:

The heart of an air conditioning heater is the refrigeration cycle, which is a continuous process that consists of four main components: the evaporator, compressor, condenser, and expansion valve. This cycle operates in both cooling and heating modes, albeit with slight variations.

a) Cooling Mode:

  • The process begins as warm indoor air is drawn into the system.
  • The refrigerant inside the evaporator coil absorbs heat from the air, causing the refrigerant to evaporate and turn into a gas.
  • The compressor then compresses the gas, raising its temperature and pressure.
  • The hot refrigerant gas moves to the condenser coil located outside the building.
  • In the condenser, the refrigerant releases the absorbed heat to the outdoor air, cooling and condensing back into a liquid.
  • The liquid refrigerant passes through the expansion valve, where its pressure decreases, preparing it to repeat the cycle.

b) Heating Mode:

  • During the heating mode, the refrigeration cycle reverses to extract heat from the outdoor air and transfer it indoors.
  • The outdoor unit acts as an evaporator, and the indoor unit acts as a condenser.
  • The outdoor unit absorbs heat from the outdoor air, even in cold temperatures, and the refrigerant evaporates.
  • The compressor increases the temperature and pressure of the refrigerant gas.
  • The heated gas flows into the indoor unit’s condenser coil, where it releases heat to the indoor air, warming the space.
  • The refrigerant then passes through the expansion valve, lowering its pressure and restarting the cycle.
  1. Supplemental Heating and Defrosting:

In extremely cold temperatures, when there is limited heat available in the outdoor air, air conditioning heaters may utilize supplemental heating to maintain comfortable indoor temperatures. This supplemental heating can be provided by electric heating elements or a backup heating system, such as a gas furnace.

Furthermore, during the heating mode, air conditioning heaters may encounter frost or ice buildup on the outdoor unit’s evaporator coil. To prevent this, a defrosting mechanism is employed. The system temporarily switches to cooling mode, directing hot refrigerant from the indoor unit to melt the ice on the outdoor coil. This cycle helps maintain optimal performance in cold climates.


Air conditioning heaters are marvels of modern technology, capable of providing efficient heating and cooling solutions throughout the year. By harnessing the principles of heat transfer and utilizing the refrigeration cycle, these systems extract heat from the outdoor air, even in chilly temperatures, to warm indoor spaces. Understanding the functionality of air conditioning heaters can help users appreciate their versatility and make informed decisions when it comes to selecting and maintaining these valuable systems for year-round comfort.