My question, Does a power supply always draw the same power from your ac outlet( ie electric bill), or does it only draw what is needed? so if i have a 650 watt psu on something that doesnt use anywhere near the power of it, does it draw less? or does it draw the same from the ac, but it is just terminated. Cause my system runs fine right now with a 500watt, but i wanna upgrade to a 680watt because of all the pretty wires n stuff lol. So, since i am not changing anything else in the system,, will my electric bill be the same?