Season-by-Season Guide: Should My Thermostat Be Set to Auto or Fan?

October 05, 2022

As the weather is cooling off, you might be concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC bills frequently add up to a big piece of your monthly electric bill. To figure out new ways to lower their HVAC bill, some people look closely at their thermostat. Is there a setting they should use to boost efficiency?

The majority of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is running during a regular cycle, what will the fan setting offer for the HVAC system? This guide can help. We’ll review just what the fan setting is and when you can use it to reduce costs during the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting signifies that the air handler’s blower fan keeps running. A few furnaces can run at a low level in this setting, but in most cases heating or cooling isn’t being made. The ‘Auto’ setting, in contrast, will run the fan over a heating or cooling cycle and turn it off once the cycle is finished.

There are benefits and drawbacks to switching on the fan setting on your thermostat, and the ideal option can depend on your personal comfort preferences.

Advantages to using the Fan/On setting:

  • You can keep the temperature in each room more uniform by enabling the fan to keep running.
  • Indoor air quality should improve since steady airflow will keep moving airborne particles into the air filter.
  • A smaller amount of start-stop cycles for the blower fan helps extend its life span. Because the air handler is typically a component of the furnace, this means you could prevent the need for furnace repair.

Downsides to switching to the Fan/On setting:

  • A constant fan will likely add to your energy expenses slightly.
  • Continuous airflow can clog your air filter up more quickly, increasing the frequency you will want to replace it.

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

During the summer, warm air may persist 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, pushing the HVAC system to work harder to keep up with the desired temperature. In serious heat, this could result in needing AC repair more often as wear and tear increases.

The reverse can take place during the winter. Cooler spaces such as a basement will hold onto cooler air, which will eventually flow into the rest of your home. Leaving the fan setting on could draw 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 try the fan/on setting, remember 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 suffers from allergies. Allergies and similar respiratory conditions can be tough on the family. Leaving the fan on should help to increase indoor air quality, helping your family breathe easier.

Your home has 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 can help minimize these changes by steadily refreshing each room’s ventilation.