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

October 05, 2022

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

Most thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a normal cycle, what can the fan setting provide for your HVAC system? This guide will help. We’ll review just what the fan setting is and whether you can use it to reduce costs over the summer or winter.

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting means that the system's blower fan remains on. A few furnaces can 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 start the fan over a heating or cooling cycle and shut it off when the cycle is complete.

There are pros and cons to switching on the fan setting on your thermostat, and the ideal option will depend on your unique comfort needs.

Advantages to using the Fan/On setting:

  • You can keep the temperature throughout your home more balanced by permitting the fan to keep running.
  • Indoor air quality will be highest since constant airflow will keep moving airborne pollutants through the air filter.
  • Fewer start-stop cycles for the system's fan helps extend its life span. Since the air handler is usually connected to the furnace, this means you could minimize the risk of needing furnace repair.

Downsides to utilizing the Fan/On setting:

  • A nonstop fan can raise your energy costs by a small margin.
  • Nonstop airflow could 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

In the summer, warm air may stick around in unfinished spaces like 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, compelling the HVAC system to run longer to keep up with the set temperature. In severe heat, this could lead to needing AC repair more quickly as wear and tear grows.

The opposite can happen 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 running could pull more cold air upward, increasing the amount of heating you need to keep warm.

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

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

Your home experiences hot and cold spots. Many homes wrestle with persistent hot and cold spots that quickly return to a temperature different from the rest of the house. The fan setting might help lessen these changes by constantly refreshing each room’s airflow.