The watts that an electric fan uses per hour ranges from 50 watts to as much as 100 watts per hour.
Larger electric fans can use as much as 200 to 300 watts per hour.
The cost to leave a fan on all day depends on the wattage of the fan.
But for example if your electric fan uses 50 watts then it would cost around $3.00 per month to leave your electric fan all day and all month.
If your fan is 100 watts then it usually costs around $6.00 to $7.50 per month depending on your electric rates.
A 50 watt electric fan will use 50 watts of electricity per hour of run time.
In 12 hours the 50 watt electric fan would use 600 watts of electricity and in 24 hours of run time the 50 watt electric fan would use 1,200 watts of electricity.
So if you run your 50 watt electric fan for 24 hours you would use 1,200 watts of electricity which would cost around 10 to 12 cents per day to run per 24 hours.
If your cost of electricity per KWH or 1,000 watts is 10 cents per KWH then the 50 watt electric fan running 24 hours per day 7 days per week for a month would cost around $3.00 per month which is cheap.
Electric fans are pretty cheap to run.
If you have 100 watt electric fan then it would cost around $6.00 to $7.20 per month to run the 100 watt fan.
If your electric fan is 200 watts then it would cost around $14.50 per month to run the electric fan 24 hours per day.
An air conditioner that uses 500 watts per hour would use 12,000 KWH per 24 hours which would cost $1.20 per day or around $36.00 per month.
Fans are cheaper to run than window air conditioners and even central air conditioners.
Central Air Conditioners can use as much as $300.00 to $400.00 per month in electricity depending on your electric rates.