When the weather starts to cool off, you may be concerned about how you’ll prepare your heating and cooling. After all, HVAC bills can add up to a significant piece of your monthly electric bill. To figure out new ways to lower their HVAC bill, some people look closely at their thermostat. Could there be a setting they could use to improve efficiency?

The bulk of thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what will the fan setting provide for an HVAC system? This guide should help. We’ll walk through precisely what the fan setting is and how you can use it to cut costs over the summer or winter.

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting signifies that the HVAC blower fan remains on. A few furnaces can operate at a low level with this setting, but in most cases heating or cooling isn’t being produced. The ‘Auto’ setting, in contrast, will run the fan over a heating or cooling cycle and turn it off after the cycle is complete.

There are advantages and disadvantages to switching on the fan setting on your thermostat, and whether you do or don’t {will|can|should]] depend on your unique comfort needs.

Advantages to trying the Fan/On setting:

  • You can keep the temperature in each room more uniform by allowing the fan to keep circulating air.
  • Indoor air quality should improve because continuous airflow will keep moving airborne contaminants 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 part of the furnace, this means you might avoid needing furnace repair.

Downsides to switching to the Fan/On setting:

  • A nonstop fan can raise your energy bills by a small margin.
  • Nonstop airflow could clog your air filter up more quickly, increasing the frequency you’ll need to replace it.

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

Through the summer, warm air may linger in unfinished spaces like the attic or an attached garage. If you use the fan setting, your HVAC system may pull this warm air into the rest of your home, compelling the HVAC system to run longer to keep up with the desired temperature. In extreme heat, this may lead to needing AC repair more regularly as wear and tear increases.

The reverse can occur over the winter. Cooler spaces such as a basement will hold onto cooler air, which may eventually flow into the rest of your home. Leaving the fan setting on may pump more cold air upward, increasing the amount of heating you need to keep warm.

If you’re still trying to decide if you should use the fan/on setting, don’t forget that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on may 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 can help to increase 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 evolve to a temperature different from the rest of the house. The fan setting might help minimize these changes by consistently refreshing each room’s supply of air.