“On” vs. “Auto” Settings

Ever wonder when it’s best to keep the fan constantly running, or to switch the setting to auto? You are not alone-many have wondered which is best. Use this guide of pros and cons of each setting to determine which setting is best for you.

Setting The Fan To “ON”

Whether the heat is on, or the house is set to cool, a setting of “on” for the fan means that it will run constantly until the setting is changed.


Keeping the fan on can help extend the life of the fan and can help evenly distribute the heat or air conditioning. The fan also pulls the air through the filter, helping clean it of dust, dirt, pet hair, and more before distributing it back through the house. Constantly running the fan ensures that the cleanest air is always running through your home.


When the fan is constantly running, even during the heat setting, it can lead to a misconception that the heat is not working properly. The temperature of the room will be accurate to its setting, but the air coming out of the vents will feel “cooler” because of the fan.

Always running the fan also means always using energy, which equals a larger bill. It also means that you will have to change the filter more often, which is another added cost.

Setting The Fan To “AUTO”

With this setting, the fan will only come on when told to by the unit. The fan will only run while the air conditioning is running, or when the heat is on, it will turn on shortly after the burners are lit and shut off when the desired temperature is met.


With the auto setting, the fan will use less energy and therefore, cost less to run. The filter won’t need to be changed as often, but then it is only because the fan isn’t filtering the air as much.


There isn’t as much of an even distribution of the air compared to the “on” setting because once the desired temperature is met the fan shuts off, no longer pushing air throughout each of the rooms.

Also, with the constant starting and stopping, there is a greater chance of wear to the fan and its gears.

Other Setting Options

If you have a newer unit, you may be able to set the fan to “constant on”, which is an energy efficient option that keeps the fan on. Another new option is “circulate”, which allows you to program the fan to turn on to even out hot or cold spots throughout the house and shut off after a few minutes.