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

October 05, 2022

Once the weather begins to cool off, you may be concerned about how you’ll make the most of your heating and cooling. After all, HVAC bills frequently contribute a big piece of your monthly electric bill. To figure out new ways to reduce costs, some people look closer at their thermostat. Could there be a setting they can use to boost efficiency?

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

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting indicates that the air handler’s blower fan remains on. Certain furnaces can run at a low level in this setting, but in general heating or cooling isn’t being produced. The ‘Auto’ setting, in contrast, will run the fan through a heating or cooling cycle and switch it off after the cycle is over.

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

Advantages to trying the Fan/On setting:

  • You can keep the temperature in every room more uniform by enabling the fan to keep running.
  • Indoor air quality can increase because constant airflow will keep forcing airborne pollutants through the air filter.
  • A smaller amount of start-stop cycles for the system's fan helps extend its life span. Since the air handler is usually connected to the furnace, this means you could minimize the risk of needing furnace repair.

Downsides to utilizing the Fan/On setting:

  • A constant fan will likely add to your energy costs somewhat.
  • Nonstop 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 may 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, compelling the HVAC system to work harder to preserve the desired temperature. In extreme heat, this can result in needing AC repair more quickly as wear and tear grows.

The reverse can happen in the winter. Cooler spaces like a basement will hold onto cooler air, which can eventually make its way into the rest of your home. Keeping the fan on may 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 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 could be best for you if:

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

Your home experiences hot and cold spots. Many homes wrestle with stubborn hot and cold spots that quickly shift to a temperature different from the rest of the house. The fan setting might help lessen these changes by constantly refreshing each room’s airflow.