I dont believe there is a program, but i know there is an electrical device which tells you the amps, voltage, watts, ect, im not sure what its called or where to get it, but i've seen them.
And when you find one, can you post here where you got it and hiw much, cause i want to get one too
lol, i found a web site that were you type in all the stuff in your system and it calculates the watts, but i dont kno if its that reliable...
here it is www.jscustompcs.com/power_supply