When the weather is cooling off, you are probably concerned about how you’ll prepare your heating and cooling. After all, HVAC bills can add up to a large portion of your monthly electric bill. To learn new ways to lower their HVAC bill, some owners look closely at their thermostat. Could there be a setting they can use to increase efficiency?

The bulk of thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what does the fan setting offer for an 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 bulk of thermostats, the fan setting means that the system's blower fan keeps running. Certain furnaces will run at a low level with this setting, but in general heating or cooling isn’t being made. The ‘Auto’ setting, in contrast, will run the fan over a heating or cooling cycle and turn it off once the cycle is finished.

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

Advantages to using the Fan/On setting:

  • You can keep the temperature in every room more balanced by enabling the fan to keep generating airflow.
  • Indoor air quality will be highest since constant airflow will keep forcing airborne pollutants through the air filter.
  • A smaller amount of start-stop cycles for the blower fan helps extend its life span. Since the air handler is often connected to the furnace, this means you can prevent the need for furnace repair.

Drawbacks to using the Fan/On setting:

  • A constant fan can raise your energy bills slightly.
  • Continuous airflow may clog your air filter up more quickly, increasing the frequency you will want to replace it.

{Choosing Between|Should My Thermostat Be on|Which Setting for My Thermostat? Fan or Auto in Summer/Winter

During the summer, warm air may persist in unfinished spaces like the attic or an attached garage. If you leave the fan on, your HVAC system might pull this warm air into the rest of your home, compelling the HVAC system to work more to maintain the desired temperature. In extreme heat, this may result in needing AC repair more quickly as wear and tear gets worse.

The reverse can happen in the winter. Cooler spaces like a basement will hold onto cooler air, which can eventually make its way into the rest of your home. Leaving the fan setting on will sometimes draw more cold air upward, increasing the amount of heating you need to remain warm.

If you’re still trying to determine if you should use the fan/on setting, keep in mind that every home and family’s comfort needs will vary. Leaving the HVAC system’s fan on could work for you if:

Someone in your household has allergies. Allergies and similar 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 has hot and cold spots. Lots of homes deal with stubborn hot and cold spots that quickly shift to a temperature different from the rest of the house. The fan setting should help lessen these changes by steadily refreshing each room’s airflow.