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

October 05, 2022

As the weather begins to cool off, you may be wondering about how you’ll make the most of your heating and cooling. After all, HVAC bills frequently add up to a big chunk of your monthly electric bill. To figure out new ways to lower their HVAC bill, some homeowners look closer at their thermostat. Could there be a setting they could use to boost 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 provide for an HVAC system? This guide will help. We’ll share precisely what the fan setting is and whether 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 system's blower fan stays on. Certain furnaces will operate at a low level with this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, conversely, will start the fan during a heating or cooling cycle and turn it off once the cycle is over.

There are advantages and disadvantages to switching on the fan setting on your thermostat, and the ideal option can depend on your distinct comfort needs.

Advantages to utilizing 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 will be highest because continuous airflow will keep passing airborne contaminants into the air filter.
  • A smaller number of start-stop cycles for the HVAC fan helps expand its life span. Because the air handler is typically connected to the furnace, this means you could minimize the risk of needing furnace repair.

Downsides to utilizing the Fan/On setting:

  • A continuous fan can add to your energy costs somewhat.
  • Nonstop airflow may clog your air filter soon, increasing the frequency you should 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 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 preferred temperature. In extreme heat, this can lead to needing AC repair more regularly as wear and tear gets worse.

The reverse can take place during the winter. Cooler spaces like a basement will hold onto cooler air, which will eventually flow into the rest of your home. Keeping the fan on may pull 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, don’t forget that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on might be ideal for you if:

Someone in your household has 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. Many 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 limit these changes by steadily refreshing each room’s airflow.