How much does a box fan cost to run?

A box fan on its low or medium setting pulls about 55 to 100 watts. At the US-average residential rate of 18.05¢/kWh from the EIA Electric Power Monthly, one hour at 100 watts costs about 1.8 cents. One hour at 55 watts costs under a penny.

The hourly number is so small that it makes the daily number small too. A 100-watt box fan running 8 hours a day costs about 14 cents a day. Running 24 hours a day, it costs about 43 cents. Even at the highest setting of 200 watts on an older model, one hour costs about 3.6 cents.

For context, a window AC running the same 8 hours pulls 500 to 700 watts and costs around 90 cents a day. A portable AC pulls 1,000 watts or more and crosses $1.50 a day. The box fan is the cheapest cooling device you can plug in.

A US box fan basically lands in one of three power tiers. The setting dial picks among them.

55 watts (low/eco): low-speed setting on most 20-inch fans. Enough airflow for a single sleeper or a desk. The quietest setting and the cheapest to run.

100 watts (medium/typical): the middle setting and the wattage most people will see most of the time. Standard 20-inch Lasko, Holmes, and Genesis fans all sit here on their medium speed.

200 watts (high/older models): the high setting on older non-PSC motors, and the top setting on larger 24-inch fans. Doubles the airflow and roughly doubles the bill, though the bill is still under a nickel an hour.

A new 20-inch fan from any major brand caps out under 120 watts on high. The 200-watt tier mostly shows up on older units or on industrial-style 24-inch fans.

The math below assumes a 90-day summer (June through August), and electricity priced at the US residential average of 18.05¢/kWh. A fan's duty cycle is effectively 1.0: when the switch is on, the motor draws power continuously.

8 hours a day (evening cooling):

55W low setting: 39.6 kWh per summer. Cost: $7.15.

100W medium setting: 72 kWh per summer. Cost: $13.00.

200W high setting: 144 kWh per summer. Cost: $26.00.

24 hours a day (constant cooling and white noise):

55W low setting: 118.8 kWh per summer. Cost: $21.45.

100W medium setting: 216 kWh per summer. Cost: $39.00.

200W high setting: 432 kWh per summer. Cost: $78.00.

The 24/7 numbers look bigger because they are tripling the runtime, not because the fan is wasteful. A 100W fan running constantly for an entire summer still costs less than $40. Most households spend more than that on a single window AC in July alone.

The same 100W box fan pulling 216 kWh across a 90-day summer costs radically different amounts depending on where you plug it in. The rate spread between cheapest and most expensive US states is 3.57x.

Louisiana (11.5¢/kWh): $25 a summer at 24/7, $8 at 8 hours a day.

Texas (14.5¢/kWh): $31 at 24/7, $10 at 8h.

US average (18.05¢/kWh): $39 at 24/7, $13 at 8h.

New York (22.85¢/kWh): $49 at 24/7, $16 at 8h.

California (31.2¢/kWh): $67 at 24/7, $22 at 8h.

Hawaii (41¢/kWh): $89 at 24/7, $30 at 8h.

Even the worst-case Hawaii number for a fan running constantly for three months is well under what a single window AC costs in any state.

All four cooling devices below have a job to do. Box fans are the cheapest by a wide margin, then ceiling fans, then tower fans, and window ACs are in a different category entirely.

Box fan (100W typical):about 2¢ an hour. 14¢ a day at 8 hours. $13 a summer. Best for moving a lot of air through a single room.

Ceiling fan (70W typical):about 1.3¢ an hour. 10¢ a day at 8 hours. $9 a summer. Best for whole-room cooling with a person in the room.

Tower fan (50W typical):about 0.9¢ an hour. 7¢ a day at 8 hours. $7 a summer. Best for narrow rooms and quiet bedrooms.

Window AC (600W typical):about 11¢ an hour. 87¢ a day at 8 hours. $60 to $180 a summer depending on size and climate. Actually drops the room temperature instead of moving air past you.

A fan only moves air. It does not lower the temperature in the room. The cooling effect is real, but it is on your skin, not on the thermometer. An AC does both: it moves air AND removes heat.

For mild summer heat under about 90°F, the cheapest cooling setup you can run is three box fans in three rooms. Total cost:

3 fans × 100W × 8 hours × 90 days = 216 kWh = $39 at US average. That is the same as ONE box fan running 24/7 all summer, and it covers three rooms instead of one.

Compare that to running a single 6,000 BTU window AC in just the bedroom: $60 to $90 over the same summer, and only the bedroom is cooled. A 12,000 BTU window AC for the living room adds another $100 to $180. The three-fan setup wins on both cost and coverage at temperatures below the low 90s.

The cutoff is around 90°F. Above that, fans alone start to feel like blowing warm air around. Below it, fans plus open windows at dusk and overnight beat any AC on a kWh basis.

The real leverage move for households that already run a window AC is not replacing the AC with fans, but adding fans to the AC. Run them together and raise the AC's setpoint.

A box fan plus a thermostat setback of 4°F gives you about the same perceived temperature. The fan moves air past your skin, the sweat evaporates faster, and the room feels 4 degrees cooler than it actually is. The AC then runs less often to hold the higher setpoint.

A 4°F summer setback typically cuts AC runtime by 10 to 15%. On a $200 summer AC bill, that is $20 to $30 saved. Add the fan cost of $13 and you net $7 to $17 in summer one. By summer two the fan is fully paid for and every dollar of AC savings is profit.

The $25 box fan is not a $25 expense. Counting AC savings, it is a $20 to $30 investment that pays back in the first year and keeps paying for the next decade.

A box fan does not cool the room. It moves air. The motor itself actually adds a small amount of heat to the room — a 100W motor dissipates 100 watts as warmth into whatever space it sits in. In an empty room with no people, a running box fan slightly raises the temperature.

The cooling effect only works if there is a person in the room for the moving air to brush against. Turn the fan off when you leave the room. Otherwise it is a 100-watt space heater with no thermostat.

A box fan also cannot dehumidify. In sticky summer air the moving air helps you feel cooler by speeding sweat evaporation, but it does not actually remove water from the air. Above about 70% relative humidity, you start needing real AC.

For the broader summer cooling math and the per-hour cost of running a window AC instead, see our piece on air conditioner cost per hour. If you want the ceiling-fan version of this comparison, see ceiling fan electricity cost. For the whole-house cooling play, our attic fan running cost piece walks through pulling cooler night air through the house.

For the full set of summer-bill tactics — when to use fans, when to run AC, when to open windows — start with how to lower your summer electric bill.

To run the math on your own fan with your local rate and runtime, use the box fan calculator.