Re: How much energy does a fan use when turned to different speeds?

The power (energy=power*time) a fan will use goes roughly as the square of 
the fan speed.  Air conditioners are a bit more difficult, as they cycle 
on and off to maintain a set temperature, but the square rule gives you 
a pretty close answer.  The only way to tell for certain is to measure 
the fan speed and note the voltage supplied and the current drawn.  With 
an air conditioner, you would have to leave it on for say, one hour and 
then spend the next hour monitoring the voltage and current drawn;  then 
you'd average over time to get the average power.

The power tag on the fan (or air conditioner) indicates the absolute 
maximum current the device will draw, usually with a blocked fan or stalled 
air conditioner.