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Should I Set My AC Fan to ‘Auto’ or ‘On’?

Take a look at your thermostat. You’ll notice two settings: auto or on. Auto means the fan in your central air system will kick on automatically when a cooling cycle begins. Conversely, the “on” mode means that the fan will run continuously, whether or not the system is cooling.

Let’s take a closer look at these settings and when you should use them.

Pros of Continuously Running Your AC Fan

Longer HVAC life: Some argue that running the AC fan has the potential to extend the life of your unit. It may not cycle on and off as frequently, which leads to less wear and tear. Take this argument with a grain of salt.

Cleaner air: Allowing your fan to remain on can improve indoor air quality. The air will be pushed through the filter, thus trapping more contaminants. This is an especially big benefit for families who suffer from asthma and allergy symptoms. The enhanced circulation will also help dehumidify your home.

Cons of Continuously Running Your AC Fan

Higher energy bills: If you do decide to leave your AC fan running, don’t be surprised to encounter higher utility bills. A 500-watt AC fan consumes almost as much energy as a refrigerator. This means you may have to pay an extra $50 a month in energy costs.

Could make your home warmer: This is obviously the biggest drawback. Between cooling cycles, the air in your ducts become warm. The fan will push this warm air into your home.

A Better Compromise

Continually running your HVAC fan can improve your indoor air quality, but it will come with a cost. If you want cleaner air, minus the steep energy bills, consider upgrading to a central air system with a variable-speed blower. This feature allows your HVAC system to cycle for longer periods of time at slower rates. That means more consistent comfort, lower humidity, and healthier air. Compared to a single-speed system, a unit with variable-speed technology is quieter and requires less than half the energy to power the fan.


For all of your cooling needs this summer, depend on AAA Service Plumbing, Heating & Electric. Call (303) 622-3449 to schedule your appointment.

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