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

October 05, 2022

Once the weather starts to cool off, you might be wondering about how you’ll make the most of your heating and cooling. After all, HVAC costs routinely make up a significant portion of your monthly electric bill. To learn new ways to reduce costs, some owners take a closer look at their thermostat. Could there be a setting they could use to improve efficiency?

The majority of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a typical cycle, what will the fan setting offer for the HVAC system? This guide can help. We’ll share just what the fan setting is and when you can use it to save money in the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting signifies that the HVAC blower fan stays on. A few furnaces will run at a low level with this setting, but in general heating or cooling isn’t being made. The ‘Auto’ setting, on the other hand, will turn on the fan during a heating or cooling cycle and shut it off after the cycle is over.

There are benefits and drawbacks to using the fan setting on your thermostat, and whether you do or don’t can depend on your unique comfort requirements.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature throughout your home more balanced by enabling the fan to keep circulating air.
  • Indoor air quality can increase since continuous airflow will keep moving airborne particles into the air filter.
  • A smaller amount of start-stop cycles for the system's fan helps lengthen its life span. Because the air handler is usually a component of the furnace, this means you could minimize the risk of needing furnace repair.

Disadvantages to utilizing the Fan/On setting:

  • A nonstop fan will likely increase your energy bills somewhat.
  • Constant airflow could clog your air filter in a shorter amount of time, increasing the frequency you’ll need to replace it.

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

In the summer, warm air can persist in unfinished spaces like the attic or an attached garage. If you leave the fan on, your HVAC system might gradually move this warm air into the rest of your home, forcing the HVAC system to run longer to preserve the desired temperature. In extreme heat, this may result in needing AC repair more quickly as wear and tear grows.

The reverse can take place in the winter. Cooler spaces like a basement will hold onto cooler air, which may eventually make its way into the rest of your home. Leaving the fan setting on will sometimes pump more cold air upward, increasing the amount of heating you need to stay warm.

If you’re still trying to determine if you should try the fan/on setting, remember that every home and family’s comfort needs are not the same. Leaving the HVAC system’s fan on could be ideal for you if:

Someone in your household has allergies. Allergies and similar respiratory conditions can be stressful on the family. Leaving the fan on should help to increase indoor air quality, helping your family breathe easier.

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