When the weather begins to cool off, you may be thinking about how you’ll prepare your heating and cooling. After all, HVAC bills can make up a big piece of your monthly electric bill. To learn new ways to reduce costs, some owners look closely at their thermostat. Is there a setting they can use to improve efficiency?

The bulk of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a regular cycle, what does the fan setting provide for an HVAC system? This guide can help. We’ll walk through just what the fan setting is and whether you can use it to cut costs in the summer or winter.

My Thermostat Has a Fan Setting?

For most thermostats, the fan setting means that the air handler’s blower fan stays on. Certain furnaces may continue to generate heat at a low level with this setting, but in most cases heating or cooling isn’t being generated. The ‘Auto’ setting, conversely, will start the fan through a heating or cooling cycle and turn it off once the cycle is complete.

There are benefits and drawbacks to switching on the fan setting on your thermostat, and what’s ideal {will|can|should]] depend on your personal comfort needs.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in every room more uniform by allowing the fan to keep circulating air.
  • Indoor air quality should improve because continuous airflow will keep forcing airborne contaminants into the air filter.
  • A smaller number of start-stop cycles for the HVAC fan helps expand its life span. Since the air handler is typically part of the furnace, this means you might minimize the risk of needing furnace repair.

Disadvantages to switching to the Fan/On setting:

  • A nonstop fan could add to your energy costs slightly.
  • Nonstop airflow may clog your air filter up more quickly, increasing the frequency you should replace it.

Which Setting for My Thermostat? Fan or Auto in Summer/Winter

Through the summer, warm air can stick around in unfinished spaces such as the attic or an attached garage. If you keep the fan running, your HVAC system might draw this warm air into the rest of your home, forcing the HVAC system to work harder to preserve the preferred temperature. In extreme heat, this could lead to needing AC repair more regularly as wear and tear gets worse.

The reverse can take place over the winter. Cooler spaces like a basement will hold onto cooler air, which may eventually flow 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 stay 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 will vary. Leaving the HVAC system’s fan on may be best for you if:

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

Your home experiences 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 should help limit these changes by constantly refreshing each room’s supply of air.