Originally Posted by TheLaughingMan
Its like this: A 500 W PSU will, at max, output 500 W. It will as JR said, adjust to the demands of whatever it is powering on the intake side as it will only draw what is needed up to 500 watts. If it is 80% effecient this means to give that 500 W it will be drawing 625 watts (120 VAC x 5.208 amps).
So my 430W psu draws at max load 120V and 10amps = 1200W
430/1200 X 100 = 36% efficiency! That blows! lol