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

October 05, 2022

When the weather starts to cool off, you are probably concerned about how you’ll make the most of your heating and cooling. After all, HVAC expenses routinely add up to a significant piece of your monthly electric bill. To figure out new ways to reduce costs, some homeowners look closely at their thermostat. Could there be a setting they can use to increase efficiency?

The majority of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a normal cycle, what will the fan setting offer for your HVAC system? This guide can help. We’ll walk through precisely what the fan setting is and whether you can use it to cut costs in the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting means that the HVAC blower fan stays on. A few furnaces may continue to operate at a low level in this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, conversely, will turn on the fan through a heating or cooling cycle and switch it off once the cycle is complete.

There are benefits and drawbacks to trying the fan setting on your thermostat, and the ideal option will depend on your personal comfort preferences.

Advantages to trying the Fan/On setting:

  • You can keep the temperature throughout your home more uniform by allowing the fan to keep circulating air.
  • Indoor air quality can increase as constant airflow will keep passing airborne pollutants into the air filter.
  • A smaller amount of start-stop cycles for the blower fan helps extend its life span. As the air handler is usually a component of the furnace, this means you could avoid needing furnace repair.

Downsides to utilizing the Fan/On setting:

  • A continuous fan could add to your energy costs somewhat.
  • Constant airflow can 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

During the summer, warm air may stick around in unfinished spaces such as the attic or an attached garage. If you keep the fan running, your HVAC system can draw this warm air into the rest of your home, pushing the HVAC system to work harder to maintain the preferred temperature. In extreme heat, this may lead to needing AC repair more often as wear and tear gets worse.

The reverse can occur in the winter. Cooler spaces such as a basement will hold onto cooler air, which can eventually make its way 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 remain warm.

If you’re still trying to determine if you should try the fan/on setting, keep in mind that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on could work 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 should help to increase indoor air quality, helping your family breathe easier.

Your home has hot and cold spots. Lots of homes deal with persistent hot and cold spots that quickly return to a temperature different from the rest of the house. The fan setting can help limit these changes by constantly refreshing each room’s ventilation.