As the weather begins to cool off, you might be concerned about how you’ll make the most of your heating and cooling. After all, HVAC costs routinely add up to a big piece of your monthly electric bill. To learn new ways to save, some people look closely at their thermostat. Maybe there’s a setting they can use to increase efficiency?

Most thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a typical cycle, what can the fan setting offer for the HVAC system? This guide can help. We’ll walk through just 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 HVAC blower fan stays on. Some furnaces may continue to generate heat at a low level with this setting, but in general heating or cooling isn’t being generated. The ‘Auto’ setting, conversely, will turn on the fan during a heating or cooling cycle and shut it off when the cycle is over.

There are pros and cons to using the fan setting on your thermostat, and what's ideal {will|can|should]] depend on your distinct comfort preferences.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in every room more balanced by permitting the fan to keep generating airflow.
  • Indoor air quality can increase as constant airflow will keep passing airborne contaminants into the air filter.
  • A smaller number of start-stop cycles for the system's fan helps lengthen its life span. Because the air handler is often part of the furnace, this means you might avoid needing furnace repair.

Downsides to using the Fan/On setting:

  • A constant fan can increase your energy costs slightly.
  • Constant airflow can clog your air filter soon, increasing the frequency you should replace it.

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

In the summer, warm air can persist in unfinished spaces like the attic or an attached garage. If you leave the fan on, 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 preferred temperature. In severe heat, this may result in needing AC repair more often as wear and tear increases.

The opposite can happen during the winter. Cooler spaces such as a basement will hold onto cooler air, which can eventually flow into the rest of your home. Keeping the fan on may 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, don’t forget that every home and family’s comfort needs will vary. Leaving the HVAC system’s fan on might be best 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 should help to improve indoor air quality, helping your family breathe easier.

Your home deals with 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 limit these changes by consistently refreshing each room’s supply of air.