Season-by-Season Guide: Should My Thermostat Run on Auto or Fan?

October 05, 2022

Once the weather starts to cool off, you might be concerned about how you’ll make the most of your heating and cooling. After all, HVAC costs can contribute a significant piece of your monthly electric bill. To try and find ways to lower their HVAC bill, some homeowners look closely at their thermostat. Is there a setting they can use to improve efficiency?

The bulk of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a normal cycle, what will the fan setting offer for your HVAC system? This guide can help. We’ll review precisely what the fan setting is and when you can use it to save money during the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting indicates that the system's blower fan remains on. Certain furnaces may continue to operate at a low level in this setting, but in most cases heating or cooling isn’t being made. The ‘Auto’ setting, on the other hand, will turn on the fan over a heating or cooling cycle and turn it off once the cycle is over.

There are benefits and drawbacks to switching on the fan setting on your thermostat, and what's ideal should depend on your personal comfort requirements.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in every room more uniform by enabling the fan to keep running.
  • Indoor air quality can increase as continuous airflow will keep moving airborne particles through the air filter.
  • A smaller number of start-stop cycles for the HVAC fan helps expand its life span. Since the air handler is typically a component of the furnace, this means you can avoid needing furnace repair.

Drawbacks to using the Fan/On setting:

  • A continuous fan could add to your energy expenses by a small margin.
  • Nonstop airflow can clog your air filter up more quickly, increasing the frequency you should replace it.

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

During the summer, warm air can linger in unfinished spaces including the attic or an attached garage. If you use the fan setting, your HVAC system can gradually move this warm air into the rest of your home, compelling the HVAC system to run longer to preserve the set temperature. In severe heat, this can result in needing AC repair more quickly as wear and tear increases.

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. Keeping the fan on could pump more cold air upward, increasing the amount of heating you need to remain warm.

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

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

Your home has hot and cold spots. All kinds of homes deal with stubborn hot and cold spots that quickly return to a temperature different from the rest of the house. The fan setting should help lessen these changes by constantly refreshing each room’s airflow.