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Should My Thermostat Fan Be on Auto or On?

The “auto” setting is handy and can save energy, but only under certain circumstances.

On Versus Automatic

With two main settings “auto” and “on”, your thermostat indicates how your HVAC blower runs. So what’s the difference?


The “auto” setting on your thermostat stands for automatic and allows your thermostat to activate your AC fan when cooling or heating. The fan will only run when your system is working to reach the set temperature.

Once at the set temperature, the fan will shut off until it’s needed again. By running your fan only when it’s needed, you can save energy and wear and tear on your blower.


Switching your thermostat to the “on” setting signals your blower fan to run constantly. Your fan will blow air continuously, even when your system isn’t heating or cooling.

Setting your fan to “on” increases airflow, pushing air through your filters more frequently to help keep your air clean and circulate air. If your home is prone to hot and cold pockets of air, this setting might be best for you.

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