Hansberger Refrigeration Blog: Your AC Repair Resource

Should Your Thermostat Fan Setting Be “On” or “Auto?”

The majority of household HVAC thermostats have individual controls for each option whether for the air conditioner, heating or the fan. There is a difference when you are choosing the setting for the fan, however. While the words don’t necessarily explain it – “on” and “auto” seem pretty imprecise – here’s the difference:

Choice 1: Switching the fan to the “on” option. This causes the thermostat fan to run continuously, no matter Should Your Thermostat Fan Setting Be "On" or "Auto?"if heating or cooling has been selected.

Positive Points

  • The air is being cleaned as it’s repeatedly drawn through the forced-air system and its filters.
  • Your fan’s life expectancy will be prolonged if it does not have to repeatedly stop and start as the A/C, heat pump or furnace cycles on and off.

Negative Points

  • It can be costly if the blower fan only has a single high speed as is the case with most basic HVAC systems.
  • The filter becomes blocked quicker, but that just means it is doing what it should. You will have to figure out how much time in between filter changes.
  • During cooler weather, you might sense “cold” air coming through your vents.

Choice 2: Setting the fan on “Auto. The fan only operates when your cooling or heating are working.

Positive Aspects

  • A decrease of energy consumption. The fan is operating less often, so it doesn’t use as much electricity.
  • Extended filter life. A filter is not having air pass through it as often, so it lasts longer.

Negative Aspects

  • Heating and cooling are dispensed unevenly as a result of the stop-and-start operation. for this reason, you may want to consider getting an HVAC system with a variable-speed blower motor; most of the time it will run nearly continuously at a slower speed while providing cooling and heating.
  • The more times your fan has to start and stop, the higher the risk of malfunctioning.

Please contact us at Hansberger Refrigeration and Electric Company for more information about cooling and heating your Yuma area home, as well as the thermostat fan.

Our goal is to help educate our customers in Yuma, Arizona about energy and home comfort issues (specific to HVAC systems). For more information about thermostat fan settings and other HVAC topics, download our free Home Comfort Resource guide.

Credit/Copyright Attribution: “Thinglass/Shutterstock”