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

October 05, 2022

When the weather starts to cool off, you are probably concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC expenses can contribute a big chunk of your monthly electric bill. To learn new ways to save, some homeowners look closely at their thermostat. Maybe there’s a setting they could use to boost 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 provide for your HVAC system? This guide will help. We’ll share what exactly the fan setting is and whether you can use it to save money in the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting signifies that the air handler’s blower fan stays on. A few furnaces may continue to operate at a low level in this setting, but in most cases heating or cooling isn’t being produced. The ‘Auto’ setting, on the other hand, will run the fan through a heating or cooling cycle and switch it off when the cycle is finished.

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

Advantages to trying the Fan/On setting:

  • You can keep the temperature in each room more uniform by permitting the fan to keep generating airflow.
  • Indoor air quality will be highest because constant airflow will keep moving airborne pollutants into the air filter.
  • A smaller amount of start-stop cycles for the system's fan helps lengthen its life span. Since the air handler is often connected to the furnace, this means you can avoid needing furnace repair.

Disadvantages to using the Fan/On setting:

  • A nonstop fan will likely increase your energy expenses slightly.
  • 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

Through the summer, warm air will sometimes stick around 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, pushing the HVAC system to work more to maintain the set temperature. In serious heat, this may result in needing AC repair more regularly as wear and tear grows.

The opposite can occur during the winter. Cooler spaces like a basement will hold onto cooler air, which may eventually drift into the rest of your home. Leaving the fan running may pull more cold air upward, increasing the amount of heating you need to keep warm.

If you’re still trying to figure out if you should try the fan/on setting, keep in mind that every home and family’s comfort needs are different. Leaving the HVAC system’s fan on could work for you if:

Someone in your household suffers from allergies. Allergies and similar respiratory conditions can be tough on the family. Leaving the fan on is more likely to enhance indoor air quality, helping your family breathe easier.

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