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Ceiling fans are the most efficient fan style for air circulation. A fan's efficacy is the efficiency rating or grade that it earns. The rating measures how much airflow is created compared to the amount of electrical energy used.
All ceiling fans have an efficiency rating that measures airflow in cubic feet per minute (CFM) per one watt (W) of electrical power used. The higher the CFM, the more energy-efficient the fan is. The most efficient ceiling fans will have a high-speed airflow rating of over 100 cubic feet per minute per watt.