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

Setting your AC fan to fully automatic

The primary benefit of using the auto setting is reducing energy consumption and utility bills. Giving the fan a break between cooling cycles reduces wear and tear, allowing you to go longer periods between preventative maintenance.

The downside of this setting is that your indoor air could grow noticeably stagnant when your AC fan isn't running, allowing dust, pet dander, pollen and other irritants to become more concentrated in the air you breathe. This is usually a bigger issue on cooler days, when your air conditioner may be between cooling cycles for extended periods.

Overall Benefits:

• Lower energy consumption
• Less maintenance
• Less noise

Leaving your AC fan in the on setting

The pro-con balance is flipped when you switch to the on setting. The AC fan blows continuously, and indoor air is filtered and replaced. While this treated air is more pleasant for everyone to breathe, it's essential for people with sensitive allergies or respiratory conditions.

Overall Benefits:

• Better airflow
• Cleaner air

On the other hand, you'll likely see a difference in your utility bills, and you'll want to be a little more productive about routine maintenance to your HVAC system. You'll also need to be diligent about replacing the air filter, which will clog up faster than it would under the auto setting. Another possible drawback: running the fan when the air conditioner isn't cooling can bring humid air inside.

On vs. auto: it's up to you

Whichever mode you prefer, the tradeoffs are clear. If you'd like more than just these two options, contact a reliable HVAC technician to inquire about equipment like variable speed blowers, which can create a middle ground for energy efficiency, or a smart thermostat, which may offer additional AC fan settings.