AC fan "auto" or "on:" which setting is better for your comfort and energy savings?   

How do these AC settings work?

Your air conditioner's fan operates independently from the cooling unit, circulating air throughout your home. When the AC fan is set to auto, it only blows when the air conditioner is actively cooling. When the fan is set to on, it blows continuously, circulating and filtering air regardless of whether the air conditioner is in cooling mode. 

Should my AC fan be set to auto or on?

The choice is yours, but each setting offers potential pros and cons.

Auto setting pros

• Typically lower AC energy consumption
• Reduced system wear and tear
• Less noise
   

Auto setting cons

• Potentially poorer circulation and air quality
• Stagnant air
• Uneven temperatures in your home
   

On setting pros

• Better overall airflow
• Cleaner air (could be important for those with allergies or respiratory conditions)
   

On setting cons

• Typically higher AC energy consumption
• More frequent filter changes and maintenance
• Potential for increased humidity if the fan runs when the AC isn’t cooling
   

Energy efficiency of fan settings

Is your goal efficiency? Lean toward the auto setting, which setting is generally more energy efficient because the fan only runs during cooling cycles, reducing electricity use and system wear. This can lead to greater cost savings over time, thanks to less energy use and less frequent system maintenance.

How fan settings affect indoor air quality

If you're concerned with air quality, setting your AC to on may be the best choice.

When set to auto, the fan may not run enough to keep air fresh, allowing dust and allergens to accumulate, especially during periods when the AC isn’t cooling. The on setting improves air circulation and filtration, which can be beneficial for indoor air quality, but may also bring in humid air if the AC isn’t actively cooling.

The best HVAC fan settings: weighing the options

Which setting is best for you? Consider the tradeoffs based on your comfort, health needs and energy goals. If you want more options, contact an HVAC professional about system enhancements like variable speed blowers or smart thermostats, which offer more nuanced control over fan settings and can help balance energy efficiency with air quality.