Once the weather is cooling off, you might be concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC costs frequently add up to a large chunk of your monthly electric bill. To figure out new ways to save, some homeowners look closely at their thermostat. Could there be a setting they could use to improve efficiency?

The bulk of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a typical cycle, what does the fan setting provide for an HVAC system? This guide will help. We’ll walk through just what the fan setting is and whether 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 system's blower fan keeps running. Certain furnaces will generate heat at a low level in this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, on the other hand, will turn on the fan during a heating or cooling cycle and switch it off after the cycle is finished.

There are pros and cons to switching on 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 each room more consistent by enabling the fan to keep circulating air.
  • Indoor air quality can increase because continuous airflow will keep moving airborne pollutants into the air filter.
  • A smaller amount of start-stop cycles for the HVAC fan helps lengthen its life span. Since the air handler is typically part of the furnace, this means you could prevent the need for furnace repair.

Downsides to using the Fan/On setting:

  • A nonstop fan will likely increase your energy costs by a small margin.
  • Constant airflow can 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

During the summer, warm air can persist in unfinished spaces including the attic or an attached garage. If you leave the fan on, your HVAC system may pull this warm air into the rest of your home, forcing the HVAC system to work more to preserve the desired temperature. In extreme heat, this may lead to needing AC repair more regularly as wear and tear grows.

The opposite can take place during the winter. Cooler spaces such as 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 stay 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 work for you if:

Someone in your household deals with allergies. Allergies and other respiratory conditions can be stressful on the family. Leaving the fan on can help to improve indoor air quality, helping your family breathe easier.

Your home deals with hot and cold spots. All kinds of homes wrestle with stubborn hot and cold spots that quickly shift to a temperature different from the rest of the house. The fan setting might help lessen these changes by constantly refreshing each room’s supply of air.