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Air Conditioner Fan On or Auto – Which Is Better?

By November 5, 2020Home Maintenance
Air conditioner fan on or auto

Living in the southern half of the U.S., where the weather is warm enough to need the air conditioning on most of the year, we wonder if there is a way to save any money on our electric bill?  We may ask ourselves, can we run the air conditioning unit less?  Or should we set the air conditioner fan to “on” or “auto” setting? The answer is, it depends on where you live. However, there are other factors to keep in mind.

Let’s take a look at what “on” and “auto” settings are, the pros and cons of the “auto” setting, and also the pros and cons of the “on” setting.


“On” setting– Fan is constantly on, even when the HVAC system is not on and is always blowing air throughout the home.

“Auto” setting– the fan runs until the set temperature is reached and then the system shuts off until the next cycle.

Pros of the “On” Setting

1. Even Distribution of Heating and Cooling in the Home

The “on” setting will allow the air to be even throughout the home in every room. Meanwhile, this does not happen with the “auto” setting.

2. The Fan is Always Running

Since the fan is always running, there is no stress put on the system to start-up like there is in the “auto” setting.

Cons of using “On” setting

1. Fan is Running Continuously in the On Setting

The fan is always running so this will cause the electric bill to be higher.

2. Blower Motor Fan Wears Out Faster in the On Setting

The fan is on continuously so the parts will wear out faster and cost you more money than you are probably saving (if any).

Air handler filter clogs
Air is constantly flowing through so the filter will become dirty or clog faster

3. The Air Handler Filter Clogs in the On Setting

Air will be flowing through it more often and will clog.  Before long, it will need to be cleaned or changed out more often.

Humidity increases in your home
Humidity in the home causes moisture on the window

4. Humidity Increases in Your Home (Especially in the South!) in the On Setting

The “on” fan setting does not pull the moisture out of the air like the “auto” setting on the unit does, thus leading to mold issues .

5. Winter Cold Air Comes In if the A/C is in the On Setting

The air from outside is pulled in with the A/C on the “on” fan setting.  Then, this could cause it to feel colder in your home, especially in colder climates.

6. Summertime Heat Comes In With the On Setting

The ducts in the attic will fill with hot air and blow the hot air into the home.  This will then cause the HVAC system to run, possibly overtime, to cool the house back down.  Then there is no gain from this.

Pros of using the auto setting
Auto setting on a Thermostat

Pros of Using the “Auto” setting

1. Energy Efficient Setting

“Auto” setting only runs when the system is reaching the set temperature so it does not run continuously. Once it reaches the set temperature, it turns off until the next cycle.

2. “Auto” Setting Acts As a Dehumidifier

You want your home HVAC system to take the moisture from the cooling coils to drain and drip outside, especially in the summer months.  This setting acts as a dehumidifier as it takes the water out of the home.

3. Cleaner Air If You Have a Filtration System or UV Lights

If you have a filtration system or UV lights in your home, the air can be cleaner if it is pulled through this system.

Cons of Using “Auto” Setting

1. Less Even Air Distribution In the Home

As the system shuts off when the set temperature is reached in the home, this does not allow for all rooms to be cooled the same

2. Start and Stop of the HVAC System

Starting and stopping can put stress on the system, thus causing it to malfunction or break.

Recommendations for Air Conditioner Fan On or Auto

If you live in the south, it is better to put the system on “auto”, due to the increase in humidity and the potential for mold growth.  In other places in the U.S., try both and see what works best for your home. 

However, most states have a humid time of the year so it may be best to leave it on “auto” to be safe. Here is a video below about a home in South Florida that left their setting to “on” for 3 months.


Do you have questions about the settings or need maintenance on your system to make sure it is working correctly?  Reply to us below and let us know!