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

October 05, 2022

Once the weather is cooling off, you might be wondering about how you’ll take full advantage of your heating and cooling. After all, HVAC bills can make up a significant chunk of your monthly electric bill. To learn new ways to reduce costs, some homeowners look closely at their thermostat. Could there be a setting they should use to boost efficiency?

The majority of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what can the fan setting provide for the HVAC system? This guide should help. We’ll share just what the fan setting is and when you can use it to reduce costs in the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting indicates that the system's blower fan remains on. A few furnaces will run at a low level in this setting, but in most cases heating or cooling isn’t being generated. The ‘Auto’ setting, on the other hand, will run the fan through a heating or cooling cycle and shut it off once the cycle is complete.

There are pros and cons to switching on the fan setting on your thermostat, and the ideal option will depend on your distinct comfort needs.

Advantages to utilizing the Fan/On setting:

  • You can keep the temperature in each room more balanced by permitting the fan to keep running.
  • Indoor air quality will be highest as steady airflow will keep forcing airborne particles into the air filter.
  • A smaller amount of start-stop cycles for the blower fan helps lengthen its life span. Since the air handler is usually part of the furnace, this means you could prevent the need for furnace repair.

Drawbacks to utilizing the Fan/On setting:

  • A constant fan will likely add to your energy expenses by a small margin.
  • Constant airflow may clog your air filter in a shorter amount of time, increasing the frequency you’ll need to replace it.

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

Through the summer, warm air will sometimes persist in unfinished spaces including 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, forcing the HVAC system to work more to keep up with the desired temperature. In severe heat, this can result in needing AC repair more regularly as wear and tear grows.

The opposite can take place in the winter. Cooler spaces like a basement will hold onto cooler air, which will eventually make its way into the rest of your home. Leaving the fan running may pump more cold air upward, increasing the amount of heating you need to keep warm.

If you’re still trying to determine if you should switch to the fan/on setting, don’t forget that every home and family’s comfort needs will vary. Leaving the HVAC system’s fan on may be best for you if:

Someone in your household has allergies. Allergies and similar respiratory conditions can be hard on the family. Leaving the fan on should help to enhance indoor air quality, helping your family breathe easier.

Your home deals with hot and cold spots. All kinds of homes wrestle with difficult hot and cold spots that quickly evolve 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.