The average floor box fan uses 100 watts of electricity. A simple method for calculating the wattage of any electrical device is to multiply the amps times the volts. This information is usually found on the back of the appliance or on a tag affixed to the cord.
As a general rule, ceiling fans use less wattage than box fans. A 42-inch ceiling fan on low speed uses only 24 watts of power. A 36-inch ceiling fan at high speed is still economical at 55 watts. A 52-inch ceiling fan on high speed supplies a tremendous amount of cooling power but only uses an affordable 90 watts of electricity.