# Fan Efficiency

There are many factors taken into account when making the selection of a ceiling fan.

The air volume flow produced by ceiling fans is important in determining the relative EFFICIENCY of the fan.

Air volume movement is measured in cubic meters per hour (m3/h) or cubic feet per minute (cfm).

1 cubic foot per minute = 1.6990108 cubic meters / hour

The air volume flow produced relative to the watts consumed gives a ratio expressed as cubic meters per hour per watt. ([m3/h]/W)

For example:

FAN A – with a flow rate of 6770 m3/h (cubic meters per hour) consuming 63 watts of power at top speed, would have an EFFICIENCY of 107.4 ([m3/h]/W).

FAN B – with a flow rate of 5892 m3/h (cubic meters per hour) consuming 60 watts of power at top speed, would have an EFFICIENCY of 98.2 ([m3/h]/W).

In this example FAN A is moving a greater volume of air and is the more efficient.

The AIR FLOW RATE is effected by the speed of the fan, but is not dependant on the speed of the fan. That is to say, just because one fan is spinning faster than another does not automatically mean it is moving more air.

Further, it may not be EFFICIENCY that is the motivator for a customer’s choice. Sometimes the AIR VOLUME may be achieved by a high power, inefficient motor – but it is the high air volume that is most import.