When the weather begins to cool off, you may be concerned about how you’ll prepare your heating and cooling. After all, HVAC costs can add up to a large piece of your monthly electric bill. To try and find ways to save, some homeowners look closer at their thermostat. Is there a setting they could use to improve efficiency?

Most thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is running during a normal cycle, what will the fan setting offer for an HVAC system? This guide can help. We’ll review what exactly the fan setting is and how you can use it to cut costs during 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 remains on. Some furnaces may continue to generate heat at a low level with this setting, but in general heating or cooling isn’t being produced. The ‘Auto’ setting, in contrast, will turn on the fan over a heating or cooling cycle and shut it off when the cycle is finished.

There are advantages and disadvantages to trying the fan setting on your thermostat, and the ideal option {will|can|should]] depend on your unique comfort preferences.

Advantages to trying the Fan/On setting:

  • You can keep the temperature throughout your home more consistent by allowing the fan to keep running.
  • Indoor air quality will be highest as continuous airflow will keep passing airborne contaminants through the air filter.
  • A smaller number of start-stop cycles for the blower fan helps extend its life span. As the air handler is often part of the furnace, this means you can prevent the need for furnace repair.

Drawbacks to utilizing the Fan/On setting:

  • A continuous fan can increase your energy costs slightly.
  • Continuous airflow can clog your air filter soon, increasing the frequency you’ll need to replace it.

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

During the summer, warm air will sometimes stick around in unfinished spaces such as the attic or an attached garage. If you keep the fan running, your HVAC system can gradually move this warm air into the rest of your home, compelling the HVAC system to work more to maintain the set temperature. In severe heat, this can result in needing AC repair more regularly as wear and tear gets worse.

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

If you’re still trying to figure out if you should switch to the fan/on setting, remember that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on might be best for you if:

Someone in your household has allergies. Allergies and similar 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 has hot and cold spots. Many homes wrestle with difficult hot and cold spots that quickly shift 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.