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Should Homeowners Set Their Thermostat to Auto or Fan On?

When you’re setting your thermostat for the HVAC system, you typically have two options: “fan on” or “auto.” Both settings have advantages and disadvantages, depending on the situation.

Using the “Fan On” Option

In this mode, the fan runs constantly, helping to circulate the air between cycles. In some cases, this can be beneficial, for the following reasons:

  • Improved air filtration – Because air is constantly moving through the filter, more contaminants are being removed from the air.
  • Better distribution of heated or cooled air – As the air keeps circulating, it tends to temper any hot or cold spots.
  • Less wear on the fan – Frequent stops and starts can shorten the life of the fan’s bearings and brushes.


Operating the fan constancy, however, can have some serious drawbacks, including:

  • High energy usage – Any time the fan is running, it uses up to 500 watts of power.
  • Less dehumidification – Any moisture left on the evaporator between air conditioning cycles can be evaporated again due to the constant airflow.
  • More filter changes – With constant use, the air filter must be changed more often.


Using the “Auto” Setting

Using this option engages the fan only when it’s required to distribute air, which offers the following advantages:

  • Less energy usage since the fan shuts down between cycles
  • Better dehumidification, as moisture on the evaporator coil drains away between cycles
  • Air filters last longer, due to less airflow


Choosing “auto” also has a few disadvantages:

  • Increased fan wear, due to frequent starts and stops
  • Less air filtration
  • Possible hot or cold spots between cycles

In most homes, the “auto” setting is the best option for efficiency and comfort, though you can have the best of both worlds by continuing to run the fan for a short time between cycles. This can be automated by some programmable thermostats.

To learn more about properly setting your thermostat, check out Pioneer Comfort System’s HVAC services, or call 318-795-8000. We serve the Shreveport, Bossier City and Natchitoches areas.

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