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

October 05, 2022

As the weather is cooling off, you might be wondering about how you’ll take full advantage of your heating and cooling. After all, HVAC costs routinely add up to a big portion of your monthly electric bill. To try and find ways to lower their HVAC bill, some people look closely at their thermostat. Maybe there’s a setting they could use to improve efficiency?

The bulk of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a normal cycle, what will the fan setting offer for your HVAC system? This guide can help. We’ll walk through what exactly the fan setting is and how you can use it to save money during the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting means that the HVAC blower fan remains on. Some furnaces may continue to operate at a low level in this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, on the other hand, will run the fan during a heating or cooling cycle and shut it off when the cycle is finished.

There are benefits and drawbacks to switching on the fan setting on your thermostat, and whether you do or don’t can depend on your unique comfort preferences.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in each room more consistent by allowing the fan to keep circulating air.
  • Indoor air quality can increase since constant airflow will keep passing airborne particles into the air filter.
  • Fewer start-stop cycles for the HVAC fan helps extend its life span. As the air handler is typically connected to the furnace, this means you might prevent the need for furnace repair.

Drawbacks to utilizing the Fan/On setting:

  • A constant fan can add to your energy bills by a small margin.
  • Nonstop airflow can clog your air filter soon, increasing the frequency you’ll need to replace it.

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

In the summer, warm air will sometimes persist in unfinished spaces such as the attic or an attached garage. If you keep the fan running, your HVAC system might draw this warm air into the rest of your home, pushing the HVAC system to work harder to maintain the preferred temperature. In serious heat, this can result in needing AC repair more regularly as wear and tear gets worse.

The reverse can take place in the winter. Cooler spaces such as a basement will hold onto cooler air, which can eventually drift into the rest of your home. Leaving the fan setting on may pump more cold air upward, increasing the amount of heating you need to keep warm.

If you’re still trying to figure out if you should use the fan/on setting, remember that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on might work for you if:

Someone in your household has allergies. Allergies and other respiratory conditions can be stressful on the family. Leaving the fan on should help to increase 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 return to a temperature different from the rest of the house. The fan setting might help limit these changes by steadily refreshing each room’s supply of air.