Should The Outside Fan Run When The Heat is On?

As winter draws closer, it’s time to make your home warm and comfortable, set the thermostat to an ambient temperature and enjoy the season. As the ideal heat exchange system, heat pumps are a convenient and cost-effective investment for your home.

With your heat pump ready, you may be wondering if the outside unit fan should run when the heat is on. 

The answer to that is yes, it should run even when the heat pump is on. The fan helps to draw the outside heat in, helping the heat pump perform efficiently. 

In this article, you’ll find answers to:

  • Should the outside fan run when the heat is on?
    • Should the outside fan run when ac is on?
  • Should I leave my heat pump on all the time?
  • Should a heat pump run constantly in the summer?

Should the outside fan run when the heat is on?

Yes, the outdoor unit fan should run when the heat is on. But why exactly? Before we answer this question in detail, let’s see how a heat pump works. 

How do Heat pumps work?

If you are familiar with the workings of Air Conditioners, you already know the basic principles on which both ACs and heat pumps function. 

Heat pump runs on the physical property of heat transfer – heat tends to travel from high temperatures to low temperatures. They consist of an indoor unit and an outdoor unit, both containing coils and a fan each.

The coils act as condensers or evaporators depending upon the heat pump operation mode. The fan helps facilitate the exchange of heat in both directions.  

During winters, in cooling mode, the heat pump captures heat from the environment – yes, even during colder months. This is made possible by creating a temperature gradient between the outdoors and the extremely cool refrigerant, running inside the outdoor unit coils (acting as evaporators). 

As a result, the refrigerant absorbs heat from outside and gets turned into hot liquid by highly pressurized coils of the indoor unit (acting as condensers). The heat from the liquid refrigerant is then distributed via ducts throughout your home turning it pleasant and warm. 

When the heat pump functions in heating mode, the role of the coils in the indoor and outdoor units as condensers and evaporators gets reversed via a reversing valve. The refrigerant captures the heat inside and following the opposite route, releases the trapped heat outdoors, effectively cooling your home. 

Should the outside fan run? 

The outside fan should be running when the heat pump is on. The fans on both ends help steer heat in either direction based on the operation of the heat pump. 

  • While operating heat pumps in cooling mode, the outside unit fan must run and facilitate the necessary heat exchange. It draws air across the coils which leads to more heat being captured by the refrigerant and consequently, more heat for your home.
  • In heating mode, the outside unit fan must run as it helps release the heat from the hot coils of the compressor, like the workings of an AC. 

In other words, it makes the whole process so much more efficient. 

Should the outside fan run when ac is on?

Yes, the outside fan should run when the AC is on. 

Air conditioners operate by absorbing the heat inside your home and releasing it outdoors. Similar to heat pumps, the outside unit fan assists in dispersing heat of the hot coils into the environment and cooling the coils down. Cooling of the coils in turn kicks off the entire process of heat transfer by the AC. 

Should I leave my heat pump on all the time?

Leaving your heat pump on all the time regardless of the weather sounds wasteful and will only rack up your heating bills. You should take any decision considering the factors discussed below.

When to leave it on:

  • You live in climates where the weather is extreme and often fluctuates.
  • Your children, pets, or elderly members stay at home for long intervals.
  • Your house tends to gather high levels of humidity or doesn’t have proper ventilation during winter.

Under the above-mentioned conditions, it’s best to leave the heat pump on instead of turning it on and off as needed. Switching it on and off frequently would put a lot of strain on the pump and lead to extensive energy usage in the process, proving counterproductive.

The best course of action would be to leave it on at a moderate or low temperature and let it work its magic while you carry on. 

When to switch it off:

  • Your house has solid insulation
  • The heat pump is not the right size for your house
  • You’ve got a smart home where you can set a timer or control the settings of the thermostat remotely.

If the heat pump’s capacity is too small for the size of your house, then the best alternative is to invest in one that would efficiently heat up your house instead of overworking the existing one. It will only lead to wastage of energy and consequently, money. For the rest of the scenarios, you could switch off the heat pump when the heat is in a pleasant range.

Should a heat pump run constantly in the summer?

In summer, the heat pump will be functioning like an AC – trying to keep your home cool by soaking up the heat inside.

It’s okay to run it constantly in the summer if your heat pump is high on efficiency ratings and saves energy by design. The compressor will be turning on and off, depending upon need and this will prevent your heat pump from overworking or overheating.

If it’s not energy efficient, then it would be wise to use it when needed and not constantly.

If your heat pump is running constantly in the summer, especially on scorching days, it may be an indication that it’s struggling to achieve the optimal temperature. It has reached its capacity and is still not able to keep up with the heating load.

In that case, it’d be best to get one that is appropriate for the size of the house. You should also get it examined by professionals for signs of wear and tear, dirt accumulation in filters or low refrigerant.


Heat pumps are effective and much more energy-friendly than furnaces or other heating arrangements. The outside unit fan should therefore run whenever the heat pump is on to add to its efficiency.

Used in conjunction with quality insulation and regular maintenance, they are an excellent investment to keep your home comfortable and at just the right amount of warmth.

NOTE FROM the author

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- Tiffany B.