Should I Set My Air Conditioner Fan to ON or AUTO?

When Running Your AC Should the Fan be Set to AUTO or ON?

We recommend that you set your fan to AUTO instead of ON, as it is the most energy-efficient option. Keeping your fan on AUTO causes the fan to run only when your AC system is actively cooling your home vs. being left on continuously.

The Difference Between the AUTO and ON settings

Both the AUTO and ON settings control the AC blower fan, which is located in the air handler (the indoor part of your AC system). The blower fan pulls warm air into the AC to be cooled, then blows the cool air back into your home.

blower fan location in an indoor ac unit

The blower fan is located in the indoor AC unit

When you select the:

  • AUTO setting, it means the fan will only turn on when your system is cooling air
  • ON setting, the fan will run non-stop—even if your AC isn’t actively cooling your home’s air

Why You Should Normally Set Your Thermostat to AUTO

Compared to the ON setting, the AUTO setting gives you benefits such as:

  • Lower energy consumption. In AUTO mode, the blower fan only runs when necessary, which cuts down your AC system’s energy usage.
  • Reduced wear and tear on AC components. Because the fan isn’t running constantly, the motor and other fan components will last longer.
  • Better dehumidification. In AUTO mode, the fan shuts off between cooling cycles. This allows more moisture from humid air inside your home to collect and drain outside, which leads to lower indoor humidity.
  • Less noise. Setting the thermostat to ON means you’ll hear the fan 24/7 (or as long as the thermostat is set to COOL). In AUTO mode, you’ll only hear the fan as it’s pushing cool air into your home. If you have a newer high-efficiency system, this will not apply to you as the fan noise is minimal in newer systems anyway.

When to Use the ON Setting

In the following situations, it may be necessary or beneficial to use the ON setting:

  • You’re cleaning your house. If you’re dusting or vacuuming your home, setting the thermostat fan setting to ON can actually help you clean. The ON setting improves air circulation, which means airborne particles like dust will be pulled into your air filter. Set your thermostat to ON while cleaning, and leave it on 15-30 minutes afterward. Then, switch your thermostat back to AUTO.
  • You’re hosting a lot of guests. Sometimes the air can feel stuffy when there are a lot of people in a confined space. Turning the thermostat fan setting to ON can help circulate fresh air, making the room feel more comfortable.

Have additional questions about your thermostat settings? Reach out to Reliable Air at (512) 580-8837 or schedule a service online.

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