Does a multi-speed fan operate at a different wattage at different speeds?
I did science.

TEST ARRANGEMENT



Fig. 1 TEST OBJECT, MEASUREMENT INSTRUMENT, AND POWER SUPPLY ARRANGEMENT.

TEST OBJECT

DIMPLEX desk fan type GDCDF30 TMB. Rated 220-240V - 50 Hz, 40 W.



Fig. 2 TEST OBJECT NAMEPLATE

MEASURING INSTRUMENT

Efergy plug-in power meter type EMS-AU. Wattmeter accuracy ±2% or ±1W.



Fig. 3 DETAIL OF MEASUREMENT INSTRUMENT



Fig. 4 MEASUREMENT INSTRUMENT NAMEPLATE

TESTING DATA

Speed setting     Power (W)     Power factor
      0              0 W             -
      1             24 W             94 %
      2             29 W            100 %
      3             35 W          100 - 97 % (flicks between these two values)


All values read off after fan was left to run on the speed setting for one minute.

CONCLUSIONS

The conclusions of this study are as follows.


Rated power of 40 W is approximate.
The settings 1, 2 and 3 do not give a linear decrease in power
consumed.


Note, I do not have the means to measure the work done by the fan on
   the air, nor the output airspeed, so I cannot speak as to the total
   efficiency of the fan in terms of electrical energy converted into
   moving air.