Should You Always Keep Your Home’s AC Fan Running?

While your air conditioner automatically cycles on and off according to temperature settings on the thermostat, the AC fan actually offers two options for circulating air inside your house: “Fan On” and “Fan Auto”. These options have differing pros and cons and potential effects on your air conditioner.

  • “Fan On” means just what it says: The system fan runs all the time, even between air-conditioning cycles.
  • “Fan Auto,” on the other hand, means the fan only runs when the AC cycles on. When the thermostat signals the air conditioner to cycle off, the fan automatically turns off too.

The question is, what’s the best setting for fan operation in your house?  To help you make your own call, here’s some comparison and contrast.

AC Fan On

This setting provides constant air circulation inside the house without interruption. Air quality may be enhanced due to continuous filtration, and constant airflow may help push cooling into stubborn hot spots.

On the negative side, running the large HVAC fan nonstop increases electrical consumption and operating costs, sometimes by as much as $50 extra per month.  Also, on hot days, continuous airflow through ductwork routed through an overheated attic or near exterior walls may pick up extra heat and circulate it into rooms while the cooling function is off.

AC Fan Auto

Indoor humidity control is more effective in “Fan Auto” mode because condensation effectively drains away from the evaporator coil during intervals when the fan cycles off. Therefore, water vapor is not blown back into the airflow, and thus, indoor humidity is reduced.  Air filters also last longer because air circulation through the filter is not continuous.

A downside of “Fan Auto” mode, however, is more wear and tear on the fan motor, caused by repeated on/off operation. Also, the interval when the fan is off may allow airborne particulates to accumulate.

Ask the experts at NisAir Air Conditioning and Heating for more about the pros and cons of keeping the AC fan running continuously.

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