Season-by-Season Guide: Should My Thermostat Be on Auto or Fan?

October 05, 2022

Once the weather starts to cool off, you may be wondering about how you’ll prepare your heating and cooling. After all, HVAC bills can add up to a big piece of your monthly electric bill. To try and find ways to reduce costs, some owners look closely at their thermostat. Is there a setting they could use to boost efficiency?

Most thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a regular cycle, what will the fan setting offer for an HVAC system? This guide can help. We’ll review precisely what the fan setting is and how you can use it to cut costs during the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting indicates that the HVAC blower fan keeps running. Some furnaces may continue to operate at a low level in this setting, but in general heating or cooling isn’t being generated. The ‘Auto’ setting, on the other hand, will run the fan over a heating or cooling cycle and shut it off once the cycle is complete.

There are advantages and disadvantages to switching on the fan setting on your thermostat, and the ideal option will depend on your unique comfort needs.

Advantages to trying the Fan/On setting:

  • You can keep the temperature throughout your home more uniform by enabling the fan to keep generating airflow.
  • Indoor air quality will be highest because continuous airflow will keep forcing airborne pollutants through the air filter.
  • A smaller amount of start-stop cycles for the HVAC fan helps lengthen its life span. As the air handler is usually connected to the furnace, this means you might minimize the risk of needing furnace repair.

Drawbacks to switching to the Fan/On setting:

  • A constant fan can add to your energy expenses slightly.
  • Nonstop airflow can clog your air filter soon, increasing the frequency you will want to replace it.

Should My Thermostat Be on Fan or Auto in Summer/Winter

During the summer, warm air can stick around in unfinished spaces such as the attic or an attached garage. If you leave the fan on, your HVAC system might draw this warm air into the rest of your home, compelling the HVAC system to work harder to preserve the set temperature. In extreme heat, this can result in needing AC repair more quickly as wear and tear grows.

The opposite can take place during the winter. Cooler spaces such as a basement will hold onto cooler air, which may eventually make its way into the rest of your home. Keeping the fan on will sometimes pump more cold air upward, increasing the amount of heating you need to stay warm.

If you’re still trying to decide if you should switch to the fan/on setting, don’t forget that every home and family’s comfort needs are not the same. Leaving the HVAC system’s fan on may work for you if:

Someone in your household deals with allergies. Allergies and other respiratory conditions can be tough on the family. Leaving the fan on can help to enhance indoor air quality, helping your family breathe easier.

Your home deals with hot and cold spots. Lots of homes deal with difficult hot and cold spots that quickly shift to a temperature different from the rest of the house. The fan setting can help limit these changes by constantly refreshing each room’s ventilation.