Cheapest Fans to Run: Watts, Cost per Hour and Why a DC Motor Pays Off

Cost per hour is watts divided by 1,000, times your rate. At 17.3 cents per kWh, 19 W is 0.33 cents an hour, 38 W is 0.66 cents, 53 W is 0.92 cents, 83 W is 1.44 cents and 120 W is 2.08 cents. Run a fan 8 hours a day for 30 days and that becomes 79 cents, $1.58, $2.20, $3.45 and $4.98 a month. Over a 120 day summer at 8 hours a day, even the 120 W box fan comes to about $20.

Your state's rate scales those numbers. A 38 W circulator for 8 hours a day for a month costs $1.08 in North Dakota at 11.81 cents, $2.68 in Connecticut at 29.38 cents and $3.70 in Hawaii at 40.59 cents. A 120 W box fan costs $3.40, $8.46 and $11.69 for the same month. Our cost to run calculator does this for any wattage at your state's rate.

The useful comparison is against cooling. The Frigidaire 5,000 BTU window AC in our database is rated at 450 W, or 7.8 cents an hour and $18.68 a month at 8 hours a day. Four 38 W fans running together come to about $6.31. A fan does not lower the room temperature. It makes you feel cooler by moving air across your skin. The US Department of Energy says a ceiling fan lets you raise the thermostat about 4 F with no loss of comfort, and moving air from any fan works the same way. That is where a fan saves real money.

On high, a DC fan and a good AC fan are close. The Vornado 683DC draws 38 W and the AC Vornado 630 draws 50 W. The gap is on low, where most fans spend the night. DC motors slow down by drawing less power, so the Vornado 533DC, 610DC and 683DC are all rated 2 W on their lowest setting, the Lasko EcoQuiet tower 2.9 W and the EcoQuiet pedestal 4 W. AC motors cannot throttle that far. The Vornado 630 still draws 34 W on low, the 660 27 W and the Lasko 2510 tower 30 W.

Over a summer of sleeping with a fan, 8 hours a night for 120 nights, a 2 W DC fan on low costs 33 cents and a 34 W AC fan on low costs $5.65. That is a real difference, but it is a few dollars, not a reason to throw out a working fan. Buy DC if you are buying anyway and run the fan on low a lot, or if you want a fan that is quiet at low speed. DC fans also usually have many more speeds, 12 on the Lasko EcoQuiet models and a stepless dial on Vornado's Energy Smart line, so you can set exactly the breeze you need instead of jumping between three.

Watts tell you the cost. CFM, cubic feet of air per minute, tells you what you get for it. Dividing one by the other from the makers' spec sheets gives about 31 CFM per watt for the Vornado 660 on high (1,638 CFM at 53 W), 26 for both the Vornado 683DC (1,008 at 38 W) and the Vornado Model 80 box fan (3,179 at 120 W), and 21 for the Lasko Cool Colors box fan (1,725 at 83 W). Tower fans trail far behind at 14 for the Lasko EcoQuiet (264 at 19 W) and about 6 for the Lasko 2510 (210 at 36 W). Makers do not all test CFM the same way, so treat these as rough comparisons.

In practice, that means a tower fan is the cheapest way to put a gentle breeze on one person, but a circulator or box fan is the cheapest way to move a whole room's air. That matters for pulling cool night air through a window or pushing AC air into a back room. A box fan in a window also beats a tower for that job by a wide margin. If you want to cool the whole house with outside air, a whole-house fan does it at a scale no portable fan can match, and our whole-house fan calculator sizes one.

Tower fans are popular in bedrooms because they are slim, oscillate and come with remotes and timers. They do not move much air, though. Lasko rates its 36 inch 2510 at 210 CFM and its 42 inch EcoQuiet at 264 CFM.

Use the timer. A 36 W tower fan left on 24 hours a day costs $4.48 a month at the national rate, against $1.49 at 8 hours. The money is small, but most people forget that a fan cools nobody in an empty room. Auto modes like the one on the Levoit Classic use a temperature sensor to slow the fan as the room cools.