The number of watts a ceiling fan uses varies depending on the fan, but is calculated by averaging the amount of energy used over a period of time.
Size and Wattage
Wattage mostly has to do with the size of the fan and its motor. Larger blades and a more powerful motor will move more air and use more watts.
Every ceiling fan is different but here are some averages: 55 watts for a 36-inch fan, 75 watts for a 48-inch fan, and 100 watts for a 56-inch fan.
Energy Star Rated Fans
Energy Star is a government program for rating efficient appliances. If your fan has an Energy Star logo (a sunburst with the words "Energy Star"), it meets the specifications.
What an Energy Star Rating Means
The Energy Star rating for a fan rates how much air it moves with one watt. At a low setting it must move 155 CFM (cubic feet of air per minute), medium 110 CFM, and high 75 CFM. The minimum airflow levels for Energy Star fans are: low 1,250 CFM, medium 2,500 CFM, and high 5,000 CFM.