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

October 05, 2022

As the weather begins to cool off, you might be thinking about how you’ll prepare your heating and cooling. After all, HVAC costs routinely add up to a big chunk of your monthly electric bill. To try and find ways to reduce costs, some homeowners look closely at their thermostat. Maybe there’s a setting they could use to boost efficiency?

Most thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a regular cycle, what will the fan setting provide for your HVAC system? This guide will help. We’ll review just what 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 majority of thermostats, the fan setting means that the HVAC blower fan keeps running. Some furnaces may continue to run at a low level with this setting, but for the most part heating or cooling isn’t being made. The ‘Auto’ setting, conversely, will start the fan during a heating or cooling cycle and turn it off when the cycle is over.

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

Advantages to utilizing the Fan/On setting:

  • You can keep the temperature throughout your home more uniform by enabling the fan to keep generating airflow.
  • Indoor air quality will be highest because constant airflow will keep passing airborne contaminants through the air filter.
  • A smaller number of start-stop cycles for the HVAC fan helps lengthen its life span. Because the air handler is usually a component of the furnace, this means you can avoid needing furnace repair.

Disadvantages to utilizing the Fan/On setting:

  • A constant fan could increase your energy bills slightly.
  • 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

Through 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 might pull this warm air into the rest of your home, forcing the HVAC system to work more to keep up with the preferred temperature. In extreme heat, this can lead to needing AC repair more quickly as wear and tear grows.

The opposite can take place over the winter. Cooler spaces such as a basement will hold onto cooler air, which can eventually flow into the rest of your home. Leaving the fan setting on may draw more cold air upward, increasing the amount of heating you need to remain warm.

If you’re still trying to decide if you should switch to the fan/on setting, don’t forget that every home and family’s comfort needs will vary. 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 stressful on the family. Leaving the fan on can help to enhance indoor air quality, helping your family breathe easier.

Your home experiences hot and cold spots. Lots of homes wrestle with stubborn hot and cold spots that quickly return to a temperature different from the rest of the house. The fan setting should help limit these changes by consistently refreshing each room’s ventilation.