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

October 05, 2022

When the weather begins to cool off, you are probably concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC expenses frequently make up a big portion of your monthly electric bill. To learn new ways to save, some owners look closer at their thermostat. Could there be a setting they could use to improve efficiency?

The majority of thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what does the fan setting offer for the HVAC system? This guide should help. We’ll walk through what exactly the fan setting is and whether you can use it to save money during the summer or winter.

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting signifies that the HVAC blower fan stays on. Some furnaces can run 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 turn on the fan over a heating or cooling cycle and switch it off once the cycle is over.

There are pros and cons to trying the fan setting on your thermostat, and the ideal option can depend on your distinct comfort preferences.

Advantages to trying the Fan/On setting:

  • You can keep the temperature in each room more consistent by allowing the fan to keep running.
  • Indoor air quality will be highest since constant airflow will keep passing airborne pollutants into the air filter.
  • A smaller number of start-stop cycles for the system's fan helps expand its life span. Because the air handler is typically part of the furnace, this means you can prevent the need for furnace repair.

Disadvantages to using the Fan/On setting:

  • A nonstop fan will likely raise your energy expenses somewhat.
  • Nonstop airflow can clog your air filter in a shorter amount of time, increasing the frequency you should replace it.

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

During the summer, warm air may persist in unfinished spaces including the attic or an attached garage. If you keep the fan running, your HVAC system might pull this warm air into the rest of your home, compelling the HVAC system to work more to preserve the set temperature. In severe heat, this could result in needing AC repair more regularly as wear and tear grows.

The opposite can occur during 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 will sometimes pull more cold air upward, increasing the amount of heating you need to stay 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 may be ideal for you if:

Someone in your household suffers from allergies. Allergies and similar respiratory conditions can be stressful on the family. Leaving the fan on is more likely to improve 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 can help lessen these changes by consistently refreshing each room’s airflow.