As the weather is cooling off, you might be thinking about how you’ll prepare your heating and cooling. After all, HVAC expenses can add up to a large chunk of your monthly electric bill. To figure out new ways to lower their HVAC bill, some people look closer at their thermostat. Could there be a setting they should use to boost efficiency?

Most thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a typical cycle, what does the fan setting provide for your HVAC system? This guide can help. We’ll share just what the fan setting is and when you can use it to cut costs during the summer or winter.

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting means that the system's blower fan remains on. Certain furnaces can operate at a low level in this setting, but in general heating or cooling isn’t being produced. The ‘Auto’ setting, conversely, will start the fan through a heating or cooling cycle and turn it off when the cycle is finished.

There are pros and cons to trying the fan setting on your thermostat, and whether you do or don’t {will|can|should]] depend on your personal comfort preferences.

Advantages to trying the Fan/On setting:

  • You can keep the temperature throughout your home more consistent by permitting the fan to keep circulating air.
  • Indoor air quality should improve because constant airflow will keep passing airborne particles through the air filter.
  • A smaller amount of start-stop cycles for the system's fan helps lengthen its life span. Because the air handler is typically part of the furnace, this means you might avoid needing furnace repair.

Downsides to switching to the Fan/On setting:

  • A nonstop fan can add to your energy expenses by a small margin.
  • Continuous 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

During the summer, warm air can persist in unfinished spaces including the attic or an attached garage. If you use the fan setting, your HVAC system may draw this warm air into the rest of your home, forcing the HVAC system to work more to keep up with the desired temperature. In serious heat, this may lead to needing AC repair more quickly as wear and tear increases.

The reverse can happen in the winter. Cooler spaces such as a basement will hold onto cooler air, which can eventually drift into the rest of your home. Leaving the fan running will sometimes pull more cold air upward, increasing the amount of heating you need to remain warm.

If you’re still trying to decide if you should try the fan/on setting, don’t forget that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on could be ideal for you if:

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

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