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

October 05, 2022

Once the weather is cooling off, you are probably concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC expenses routinely add up to a large piece of your monthly electric bill. To learn new ways to save, some people take a closer look at their thermostat. Is there a setting they should use to increase efficiency?

The majority of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is running during a regular cycle, what can the fan setting offer for your 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 the majority of thermostats, the fan setting indicates that the HVAC blower fan remains on. Certain furnaces may continue to generate heat at a low level with this setting, but in general heating or cooling isn’t being produced. The ‘Auto’ setting, on the other hand, will start the fan through a heating or cooling cycle and switch it off after the cycle is finished.

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

Advantages to using the Fan/On setting:

  • You can keep the temperature in every room more uniform by allowing the fan to keep circulating air.
  • Indoor air quality will be highest as steady airflow will keep moving airborne contaminants through the air filter.
  • A smaller amount of start-stop cycles for the HVAC fan helps extend its life span. Since the air handler is typically part of the furnace, this means you might prevent the need for furnace repair.

Downsides to using the Fan/On setting:

  • A constant fan could increase your energy expenses by a small margin.
  • Constant airflow could 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

In the summer, warm air can stick around in unfinished spaces like the attic or an attached garage. If you keep the fan running, your HVAC system might gradually move this warm air into the rest of your home, pushing the HVAC system to work more to maintain the set temperature. In severe heat, this may result in needing AC repair more quickly as wear and tear increases.

The opposite can occur during the winter. Cooler spaces like a basement will hold onto cooler air, which will eventually flow into the rest of your home. Leaving the fan setting on may pull more cold air upward, increasing the amount of heating you need to keep warm.

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

Someone in your household suffers from allergies. Allergies and other respiratory conditions can be hard on the family. Leaving the fan on is more likely to enhance indoor air quality, helping your family breathe easier.

Your home experiences hot and cold spots. Lots 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 can help minimize these changes by steadily refreshing each room’s supply of air.