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

October 05, 2022

Once the weather is cooling off, you might be concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC bills routinely add up to a large piece of your monthly electric bill. To learn new ways to reduce costs, some owners look closely at their thermostat. Maybe there’s a setting they should use to improve efficiency?

The majority of thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is running during a normal cycle, what can the fan setting offer for your HVAC system? This guide should help. We’ll share just what the fan setting is and whether you can use it to cut costs over the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting means that the air handler’s blower fan stays on. Certain furnaces may continue to run at a low level in this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, in contrast, will run the fan during a heating or cooling cycle and turn it off once the cycle is finished.

There are pros and cons to switching on the fan setting on your thermostat, and the ideal option should depend on your personal comfort preferences.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in each room more balanced by enabling the fan to keep circulating air.
  • Indoor air quality can increase since steady airflow will keep passing airborne particles through the air filter.
  • Fewer start-stop cycles for the HVAC fan helps expand its life span. Since the air handler is usually connected to the furnace, this means you might prevent the need for furnace repair.

Disadvantages to switching to the Fan/On setting:

  • A nonstop fan could add to your energy costs somewhat.
  • Constant airflow may 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

Through the summer, warm air may persist in unfinished spaces including the attic or an attached garage. If you use the fan setting, your HVAC system may gradually move this warm air into the rest of your home, compelling the HVAC system to run longer to preserve the preferred temperature. In extreme heat, this could lead to needing AC repair more regularly as wear and tear gets worse.

The opposite can occur over the winter. Cooler spaces like a basement will hold onto cooler air, which can eventually flow into the rest of your home. Leaving the fan setting on could 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, keep in mind that every home and family’s comfort needs will vary. Leaving the HVAC system’s fan on could be ideal for you if:

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

Your home deals with hot and cold spots. All kinds of homes wrestle with persistent hot and cold spots that quickly evolve to a temperature different from the rest of the house. The fan setting should help lessen these changes by steadily refreshing each room’s ventilation.