The power cord that supplies the box is an "air conditioner" cord, so it can easily take the current drawn by the popper.

I usually start with the fan on "full-blast", and the heater set to about "100 volts" (higher if it's cold out).  As roasting proceeds, I adjust the fan speed down, to keep the beans "rolling" but not "jumping". I increase the voltage to the heater in order to get the desired temperature ramp.  Typically I'll push the voltage up 2 or 3 times during the roast, and may reduce it near the end to get a slower finish.