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

October 05, 2022

As the weather begins to cool off, you might be wondering about how you’ll make the most of your heating and cooling. After all, HVAC expenses can add up to a large chunk of your monthly electric bill. To try and find ways to reduce costs, some owners look closely at their thermostat. Could there be a setting they could use to improve efficiency?

The bulk of thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is running during a normal cycle, what will the fan setting offer 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 during the summer or winter.

What Is the Fan Setting on My Thermostat?

For most thermostats, the fan setting means that the HVAC blower fan keeps running. Some 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 during a heating or cooling cycle and turn it off after the cycle is over.

There are advantages and disadvantages to trying the fan setting on your thermostat, and what's ideal will depend on your distinct comfort requirements.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature in each room more consistent by permitting the fan to keep generating airflow.
  • Indoor air quality should improve since continuous airflow will keep moving airborne pollutants through the air filter.
  • A smaller number of start-stop cycles for the system's fan helps expand its life span. As the air handler is often part of the furnace, this means you could prevent the need for furnace repair.

Disadvantages to utilizing the Fan/On setting:

  • A continuous fan can add to your energy expenses somewhat.
  • Nonstop airflow may 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 can stick around in unfinished spaces such as the attic or an attached garage. If you use the fan setting, your HVAC system can draw this warm air into the rest of your home, pushing the HVAC system to work harder to preserve the preferred temperature. In extreme heat, this can result in needing AC repair more regularly as wear and tear gets worse.

The opposite can take place in the winter. Cooler spaces like a basement will hold onto cooler air, which can eventually drift 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 decide if you should switch to the fan/on setting, don’t forget that every home and family’s comfort needs are not the same. Leaving the HVAC system’s fan on might be best for you if:

Someone in your household deals with allergies. Allergies and similar respiratory conditions can be stressful 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. Many homes wrestle with difficult hot and cold spots that quickly evolve to a temperature different from the rest of the house. The fan setting can help limit these changes by consistently refreshing each room’s airflow.