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

October 05, 2022

When the weather is cooling off, you might be thinking about how you’ll prepare your heating and cooling. After all, HVAC bills frequently make up a significant portion of your monthly electric bill. To learn new ways to lower their HVAC bill, some owners take a closer look at their thermostat. Is there a setting they can use to boost efficiency?

The majority of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what will the fan setting offer for your HVAC system? This guide should help. We’ll review precisely what the fan setting is and when you can use it to reduce costs during the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting signifies that the system's blower fan keeps running. A few furnaces will generate heat at a low level in this setting, but in most cases heating or cooling isn’t being produced. The ‘Auto’ setting, conversely, will turn on the fan during a heating or cooling cycle and switch it off when the cycle is finished.

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

Advantages to using the Fan/On setting:

  • You can keep the temperature in each room more uniform by enabling the fan to keep generating airflow.
  • Indoor air quality should improve as steady airflow will keep moving airborne contaminants into the air filter.
  • A smaller number of start-stop cycles for the system's fan helps extend its life span. Because the air handler is often a component of the furnace, this means you could minimize the risk of needing furnace repair.

Drawbacks to using the Fan/On setting:

  • A nonstop fan will likely add to your energy expenses somewhat.
  • Nonstop airflow can clog your air filter soon, increasing the frequency you will want to replace it.

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

Through the summer, warm air can linger in unfinished spaces like 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 more to keep up with the preferred temperature. In severe heat, this can lead to needing AC repair more often 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 may eventually drift into the rest of your home. Leaving the fan running will sometimes draw 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, remember 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 other respiratory conditions can be hard on the family. Leaving the fan on can help to improve indoor air quality, helping your family breathe easier.

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