https://old.rosieonthehouse.com/faqs/what-kind-of-ceiling-fan-is-most-energy-efficient

What kind of ceiling fan is most energy-efficient?

Several of a ceiling fan’s components determine how energy efficient it is. When you’re buying, consider:

“The best way to compare ceiling fans from one model to the next would be by comparing the CFMs of each fan. This stands for Cubic Feet per Minute. The higher the CFM rating, the better or more air movement you are going to get. The manufacturers take into account motor size, blade pitch, blade size and motor RPM to determine their CFM rating. You can find a three-blade fan that has a higher CFM rating than a five-blade fan simply because of a better motor or better blade pitch. Also, vice versa, you can find a five- or six blade fan that pushes more air than a three-blade fan as well. By comparing CFM’s, you are getting a good idea of the effectiveness of the air movement you are going to receive because it weighs all the factors when combined in one unit,” says Ashley Childers, Statewide Lighting, a Rosie-Certified Partner.
The pitch of the blades. Some say the ideal fan has five blades at a 15-degree pitch. The pitch is the angle of the blade in relation to the motor. The greater the pitch, the more air the blade moves. You can buy fans with a pitch as high as 23 degrees, but it might be a bit noisy. Also, curved blades move more air than flat blades.
The speed of the motor. A small, inexpensive motor won’t create as much air movement as a larger motor. Before you buy, listen to the fan in action so you can hear if the motor makes too much noise for you. A quality fan should not be noisy.
The distance between the fan and the ceiling. For the most comfortable results, install the fan seven to eight feet from the floor. If your room has high ceilings, buy an extension “down-rod” to lower the fan to the ideal location.

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