Almot wrote:
Watts = volts * amps. If something is rated 800W 120V, it means it draws 7 amps at 120V.
took me 40 years to figure this out and I have a certificate that says I know something about electronics,, But that is very simply wrong.
Watts = Volts * amps * power factor in an A/C circuit
(You are correct in a DC circuit)
So if it says it is 800 watts at 120 volt it may well draw not 7 but 8, or 9 amps.. 
I have seen power factors in the line of .8 (80%) but I have heard of power factors as low as near zero.. (I know the technician who fixed it you see and actually saw the machine that suffered that)
The thing was drawing amps, and you could see the watts, but the motor did not turn at all... one condenser (Capacitor) from the technician's junk box and wood was sawed.