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

October 05, 2022

Once the weather starts to cool off, you may be wondering about how you’ll prepare your heating and cooling. After all, HVAC bills routinely make up a large piece of your monthly electric bill. To try and find ways to reduce costs, some owners look closer at their thermostat. Maybe there’s a setting they should use to improve efficiency?

The majority of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a typical cycle, what can the fan setting provide for your HVAC system? This guide will help. We’ll review precisely what the fan setting is and when you can use it to reduce costs over the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting indicates that the HVAC blower fan remains on. Some furnaces will generate heat at a low level with this setting, but for the most part heating or cooling isn’t being made. The ‘Auto’ setting, on the other hand, will run the fan over a heating or cooling cycle and turn it off once the cycle is finished.

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

Advantages to trying the Fan/On setting:

  • You can keep the temperature in every room more consistent by enabling the fan to keep generating airflow.
  • Indoor air quality should improve because steady airflow will keep passing airborne contaminants into the air filter.
  • Fewer start-stop cycles for the blower fan helps expand its life span. Since the air handler is typically part of the furnace, this means you could minimize the risk of needing furnace repair.

Disadvantages to utilizing the Fan/On setting:

  • A constant fan could add to your energy bills somewhat.
  • Nonstop airflow may 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

In the summer, warm air will sometimes linger in unfinished spaces including the attic or an attached garage. If you use the fan setting, your HVAC system may gradually move this warm air into the rest of your home, forcing the HVAC system to run longer to preserve the preferred temperature. In serious heat, this could lead to needing AC repair more often as wear and tear gets worse.

The reverse can occur over the winter. Cooler spaces like a basement will hold onto cooler air, which may eventually make its way into the rest of your home. Keeping the fan on may draw 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 are different. Leaving the HVAC system’s fan on could work for you if:

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

Your home has 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 should help limit these changes by consistently refreshing each room’s ventilation.