On Or Auto: Which is the Better Thermostat Setting?

If you have ever wondered which is the better thermostat setting for the fan mode, you are probably not alone. Though, while not affecting indoor temperatures so much like "heat" and "cool" modes, the fan "on" and fan "auto" settings do impact indoor air quality, energy bills and more.

Thermostat Fan Settings

The fan setting controls the blower motor after "heat" and "cool" modes turn off. For example, if you have the fan mode in the "auto" position, the blower will turn off when "heat" and "cool" modes end. Or, if "heat" and "cool" modes are not on at all, the fan mode will be off, too.

If you have the fan mode in the "on" position, the blower will continue to run, circulating unconditioned air through your home, after "heat" and "cool" modes come to an end.

Choosing Fan Modes

Consider how the fan mode you choose affects indoor air quality, energy bills and more:

  • Indoor air quality: The "on" fan mode pulls airflow through the furnace filter when your furnace and A/C are off. This is beneficial if anyone in your home suffers respiratory ailments. Additionally, turn on the fan when you are house cleaning to help remove stirred-up dust from indoor air (i.e. when "heat" and "cool" are not on).

  • Comfort: During the heating months, the thermostat's "on" mode can help continually circulate indoor air more evenly. Though, this also depends on where your vents are located (i.e. wind-chill effect).

  • Energy efficiency: Continuous use of the HVAC blower is going to increase your energy bills. The better thermostat setting and alternative to circulating indoor air is to use ceiling fans. Reverse the switch on your ceiling fans so that airflow is pulled up toward the ceiling. Moreover, ceiling fans are quieter and use a fraction of electricity as your HVAC blower.