Measured Ceiling Fan Performance and Usage Patterns: Implications for Efficiency and Comfort Improvement

Simulations suggest residential cooling energy use can be reduced up to 15% through the use of ceiling fans with thermostat set-up. However, monitoring data from a large scale study of Florida homes found that air conditioning consumption was not lower because thermostats settings were not raised in response to fan use, and many fans were apparently left on for long periods in unoccupied zones. To further study these findings, we collected field data on actual ceiling fan usage patterns and how they might be affected by education. We also studied power characteristics and air moving efficiency of current generation ceiling fans and a prototype improved fan. Field tests were performed in two occupied Miami homes. Time-of-use loggers were installed on the five ceiling fans in each home and left in place for a year. In one household, no specific information was given on recommended fan operation; in the other, members were informed about the best operation strategy. Monitoring revealed large differences in fan energy use; the informed household used approximately 175 kWh per year to operate fans (average 2.7 hours on per day per fan) as opposed to 810 kWh in the uninformed home (12.6 hours per day per fan). Secondly, a test room was set-up where ceiling fan power use, rpm and airflow underneath the fan could be measured. Three ceiling fans of various types were evaluated. Results revealed a) power use of the fans varied from 7 93 W depending on model and motor speed and b) measured air velocity profile dropped off sharply beyond the fan blade diameter. Using measured performance, we estimated the combined motor and fan efficiencies at less than 5%. However, the prototype improved fan showed a significant air velocity to power use ratio improvement. Our results indicate significant potential benefits from consumer education as well as a large potential for improvement of ceiling fan efficiency.