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

October 05, 2022

As the weather starts to cool off, you are probably wondering about how you’ll take full advantage of your heating and cooling. After all, HVAC expenses can make up a large portion of your monthly electric bill. To figure out new ways to reduce costs, some owners look closer at their thermostat. Maybe there’s a setting they could use to improve efficiency?

The majority of thermostats include both a ‘Fan’ or ‘Fan On’ setting. But if the fan is going during a normal cycle, what can the fan setting provide for the HVAC system? This guide can help. We’ll share just what the fan setting is and when you can use it to cut costs during the summer or winter.

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting signifies that the system's blower fan keeps running. A few furnaces will operate at a low level with this setting, but in general heating or cooling isn’t being generated. The ‘Auto’ setting, on the other hand, will turn on the fan during a heating or cooling cycle and switch it off when the cycle is over.

There are pros and cons to trying the fan setting on your thermostat, and what's ideal can depend on your personal comfort needs.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in every room more consistent by enabling the fan to keep running.
  • Indoor air quality will be highest as continuous airflow will keep moving airborne pollutants into the air filter.
  • Fewer start-stop cycles for the system's fan helps extend its life span. Because the air handler is usually a component of the furnace, this means you can prevent the need for furnace repair.

Drawbacks to utilizing the Fan/On setting:

  • A constant fan could increase your energy costs slightly.
  • Nonstop airflow can 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

During the summer, warm air will sometimes stick around in unfinished spaces including the attic or an attached garage. If you leave the fan on, your HVAC system may gradually move this warm air into the rest of your home, forcing the HVAC system to run longer to maintain the set temperature. In severe heat, this can lead to needing AC repair more regularly as wear and tear increases.

The reverse can occur during 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 running will sometimes pump 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 use the fan/on setting, remember that every home and family’s comfort needs will vary. Leaving the HVAC system’s fan on might be ideal for you if:

Someone in your household suffers from allergies. Allergies and other 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 has hot and cold spots. Many homes wrestle with difficult hot and cold spots that quickly return to a temperature different from the rest of the house. The fan setting can help minimize these changes by consistently refreshing each room’s supply of air.