AC Fan Set to "On" or "Auto" Mode: Which Saves More on Energy Bills?

Discover the optimal AC fan mode for energy savings. Get expert insights from Sandium on choosing between On and Auto mode.

Updated on Jul 26, 2023
5 min read
AC Fan Set to "On" or "Auto" Mode: Which Saves More on Energy Bills?

When it comes to optimizing energy efficiency and saving money on your air conditioning bills, the setting of your AC fan plays a crucial role. Most thermostats offer two fan settings: "On" and "Auto." But which mode is more energy-efficient and cost-effective? Let's explore the differences between the two and determine which option can help you achieve the best balance between comfort and savings.

"On" Mode:

When the AC fan is set to "On" mode, the fan operates continuously, regardless of whether the cooling system is actively running or not. This means that air is constantly circulating throughout your home, providing a consistent airflow and filtration.


  • Improved indoor air quality: Continuous air circulation helps filter out dust, allergens, and other airborne particles more effectively, leading to better indoor air quality.
  • Eliminates temperature variances: With the fan running constantly, the temperature remains more consistent throughout your home, minimizing hot or cold spots.


  • Higher energy consumption: Running the fan continuously can lead to increased energy consumption. The fan uses electricity even when the cooling system is not actively cooling the air.
  • Increased wear and tear: Constant operation can cause additional strain on the fan motor, potentially leading to more frequent maintenance and repairs.

"Auto" Mode:

In "Auto" mode, the fan operates only when the cooling system is actively running. Once the desired temperature is reached and the cooling cycle completes, the fan automatically shuts off until the next cooling cycle begins.


  • Energy savings: The fan operates only when necessary, resulting in lower energy consumption compared to the continuous operation in "On" mode.
  • Reduced wear and tear: The fan motor has regular periods of rest, reducing the strain and potential wear on the motor, which can extend its lifespan.


  • Potential temperature variances: Since the fan only runs during cooling cycles, there might be slight temperature variances between cycles. This can result in minor fluctuations in comfort levels, especially in larger homes or multi-level properties.

Choosing the Right Setting:

To determine which fan setting is best for you, consider the following factors:

  • Comfort preferences: If consistent airflow and temperature are crucial to your comfort, the "On" mode might be more suitable for you. However, keep in mind that the temperature variances in "Auto" mode are usually minimal and may not significantly impact your comfort.
  • Energy-saving goals: If your primary focus is reducing energy consumption and lowering your utility bills, "Auto" mode is the recommended option. It ensures the fan operates only when necessary, leading to potential energy savings.
  • Indoor air quality concerns: If you or your household members have respiratory issues or allergies, the continuous air circulation in "On" mode can help filter out airborne particles more effectively, leading to improved indoor air quality.
  • Home size and insulation: Larger homes or properties with multiple levels may benefit from the continuous airflow in "On" mode, as it helps maintain a more consistent temperature throughout the entire space. However, well-insulated homes may experience minimal temperature variances in "Auto" mode.


“Auto” Mode Usually Offers a Better Balance.

While both "On" and "Auto" fan settings have their advantages and considerations, "Auto" mode typically offers a better balance between energy savings and comfort. It allows the fan to operate only when necessary, reducing energy consumption and minimizing wear and tear on the fan motor. However, personal preferences and specific circumstances should also be taken into account. Consider consulting with an HVAC professional to assess your unique needs and determine the most suitable fan setting for your home.

Join the Future of Home Comfort

Take the first step towards comfortable, energy-efficient, and stress-free living by scheduling a consultation with Sandium.