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

October 05, 2022

Once the weather is cooling off, you are probably wondering about how you’ll make the most of your heating and cooling. After all, HVAC expenses routinely make up a large chunk of your monthly electric bill. To try and find ways to lower their HVAC bill, some people take a closer look at their thermostat. Maybe there’s a setting they should use to boost efficiency?

The bulk of thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a normal cycle, what can the fan setting offer for the HVAC system? This guide will help. We’ll share precisely what the fan setting is and how you can use it to reduce costs during the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting signifies that the system's blower fan keeps running. Certain furnaces will run at a low level with this setting, but in most cases heating or cooling isn’t being made. The ‘Auto’ setting, on the other hand, will start the fan through a heating or cooling cycle and shut it off when the cycle is complete.

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

Advantages to utilizing the Fan/On setting:

  • You can keep the temperature in each room more uniform by permitting the fan to keep circulating air.
  • Indoor air quality will be highest as continuous airflow will keep moving airborne contaminants through the air filter.
  • A smaller amount of start-stop cycles for the HVAC fan helps extend its life span. As the air handler is usually connected to the furnace, this means you could minimize the risk of needing furnace repair.

Disadvantages to utilizing the Fan/On setting:

  • A nonstop fan could raise your energy expenses somewhat.
  • Nonstop airflow could clog your air filter in a shorter amount of time, increasing the frequency you will want to replace it.

Should My Thermostat Be on Fan or Auto in Summer/Winter

In the summer, warm air will sometimes persist in unfinished spaces like the attic or an attached garage. If you keep the fan running, your HVAC system may draw this warm air into the rest of your home, compelling the HVAC system to work more to maintain the set temperature. In extreme heat, this could result in needing AC repair more quickly as wear and tear grows.

The reverse can take place during the winter. Cooler spaces like a basement will hold onto cooler air, which will eventually make its way into the rest of your home. Keeping the fan on could 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 try the fan/on setting, remember that every home and family’s comfort needs are not the same. Leaving the HVAC system’s fan on might be ideal for you if:

Someone in your household suffers from allergies. Allergies and similar 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 deals with hot and cold spots. Lots of homes deal with difficult hot and cold spots that quickly evolve to a temperature different from the rest of the house. The fan setting should help lessen these changes by consistently refreshing each room’s ventilation.