Should I Set My AC Fan to On or Auto?

Had a peek at your thermostat and wonder whether you should leave your AC on auto? AC auto mode means the fan only runs when the air conditioner is on, which is the most common setting in most homes. But there are reasons you might turn the fan on all the time.

This blog covers:

How the AC fan works in auto mode
How the AC fan works when set to on
Pros and cons of auto mode
Pros and cons of on
Which AC fan setting is best for your home

Keep reading to learn more about fan on vs. auto.

Key Takeaways

The default setting for most people is AC on auto, which means the fan isn’t blowing all the time.
Leaving the fan blowing all the time does have a slight impact on your utility costs.
In some cases, setting your AC to fan on can increase air movement in the home, reducing stuffiness.

Get Expert AC Advice from Elliot Services

If your AC isn’t keeping up with the heat, it might be time for professional AC maintenance service. Consider calling Elliot Services for an inspection before resorting to turning your fan on all the time.

Request Service

How the AC Fan Works in Auto Mode

When your fan is set to AC auto, it only blows when the air conditioner is actively cooling your home. Here’s how it works:

You set the thermostat to the desired temperature
Then, when the temps in the house rise above that, the thermostat signals your AC to cool
The blow fan turns on at the same time to circulate the cooled air
When the temperature falls back down to your desired level, the AC compressor and fan both shut off

Auto fan mode is the default setting in most homes because it ensures cooled air is circulated while reducing overall power draw and energy expenses.

How the AC Fan Works When Set to On

If you set the fan to on, your blower will keep running even when the AC isn’t actively cooling air. That means you’ll get air blowing out of your vents all the time, but it won’t always be cool air. When the thermostat signals that it’s time to cool your home, the AC runs as normal; the fan keeps running afterward.

Homeowners often use the on setting to circulate air more effectively throughout the home, especially if one room is consistently warmer than others.

Pros and Cons of Auto Mode

The benefits of the AC auto setting include:

Lower overall energy costs, because you aren’t powering a fan 24 hours a day
Reduced wear and tear on the blower motor, as it only runs when the AC is cooling the house
Lower humidity, as AC units are typically better at removing moisture from the air when the fan stops between cycles

Stopping airflow between cooling cycles has a few potential drawbacks. If it’s not especially hot outside, your AC may not come on enough to keep rooms from getting stuffy. Areas in the home farthest away from the thermostat may not feel as comfortably controlled as other rooms.

Pros and Cons of On

Continuous air circulation is the biggest benefit of leaving the fan on. You may notice that temperatures between rooms are more even, and you get constant movement of air through the filter in your system. That additional filtration can improve air quality.

On the other hand, moving more air through the filter means you might have to change or clean it more often, adding to the cost of maintaining your HVAC system. The fan running constantly increases overall utility costs, and if you’re in a humid climate, you may circulate more moisture into your house.

Which AC Fan Setting Is Best for Your Home

Whether or not your AC fan should be set to on or auto on depends on your personal preferences and home. Auto is best in most cases, and is the go-to choice when energy efficiency matters. If airflow is uneven in your home or you like the idea of extra filtration, consider setting your fan to on.

Before you decide, consider talking to an HVAC professional. Most recommend auto on as the standard setting, and if your HVAC isn’t performing as desired, an AC repair may provide more benefit than running the fan all the time.