How Much Does It Cost to Run a Box Fan?

A 20 inch box fan is a simple AC induction motor and a plastic blade in a square frame. On high a typical model draws about 55 to 100 W, and on low 35 to 60 W. The Lasko Cool Colors model we list, for example, is rated 56 to 83 W. High-velocity models like the Vornado Model 80 move about 3,000 cubic feet per minute and draw up to 120 W. The default here is 75 W for 8 hours, 0.6 kWh, about 10 cents a day at the national average rate.

A box fan moves more air per dollar than almost anything, but it moves air, it does not cool it. Like a ceiling fan it makes you feel cooler by speeding up evaporation from your skin. Pointed at you it can let you set the air conditioner several degrees higher. Running in an empty room it only adds its own motor heat.

Where a box fan really earns its keep is in a window. On summer nights when the outdoor air drops below the indoor temperature, a fan in one window blowing out, with another window open across the house, pulls cool air through every room. That is a whole house fan on a small scale, and it can replace hours of air conditioning in dry climates and on cool nights. Box fans rated window safe have sealed motors for this.

The motor is where the newer designs save. DC motor fans and air circulators draw 2 to 40 W across their speed range and often move comparable air at lower speeds. A box fan on low is already cheap, but a DC fan at 20 W costs about a quarter of a 75 W box fan on high.

Over a year at 8 hours a day the default uses about 219 kWh, roughly $38. Most people only run a box fan for the summer months, so the real number is usually $10 to $15. A plug-in meter gives the exact draw for each speed setting.