As the weather starts to cool off, you are probably thinking about how you’ll take full advantage of your heating and cooling. After all, HVAC costs can contribute a big piece of your monthly electric bill. To figure out new ways to reduce costs, some people look closely at their thermostat. Maybe there’s a setting they could use to improve efficiency?

The majority of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what can the fan setting provide for your HVAC system? This guide should help. We’ll walk through what exactly the fan setting is and how you can use it to save money over the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting indicates that the air handler’s blower fan remains on. Some furnaces can run at a low level with this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, in contrast, will run the fan during a heating or cooling cycle and switch it off once the cycle is finished.

There are benefits and drawbacks to trying the fan setting on your thermostat, and what's ideal {will|can|should]] depend on your unique comfort requirements.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature throughout your home more consistent by permitting the fan to keep running.
  • Indoor air quality should improve because steady airflow will keep passing airborne pollutants into the air filter.
  • Fewer start-stop cycles for the blower fan helps extend its life span. Because the air handler is typically part of the furnace, this means you could prevent the need for furnace repair.

Disadvantages to using the Fan/On setting:

  • A nonstop fan will likely increase your energy bills slightly.
  • Constant airflow may clog your air filter in a shorter amount of time, increasing the frequency you should replace it.

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

Through the summer, warm air can persist in unfinished spaces like the attic or an attached garage. If you use the fan setting, your HVAC system can gradually move this warm air into the rest of your home, pushing the HVAC system to work harder to keep up with the set temperature. In extreme heat, this could lead to needing AC repair more quickly as wear and tear grows.

The reverse can happen over the winter. Cooler spaces such as a basement will hold onto cooler air, which will 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 keep warm.

If you’re still trying to figure out if you should use the fan/on setting, keep in mind that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on may be ideal 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 can help to enhance indoor air quality, helping your family breathe easier.

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