Actually its right and wrong. PC's PSUs use "Fast Switching" meaning in an AC current you have a sign wave going from 180°(240v) to -180° (-240v) Hence the name Alternating current, Anyway a PSU uses the 0° to 180° and then switches off (so to say) and misses the rest until the sign wave returns to 0°. Thus you get DC because its only using the positive side of the sign wave so it only flows one way.
OK now the Fast switching also acts as a transformer to step down the voltage for the rails ect (wont get into to much detail)..
Now if you have a PSU of 600W and you only drawing 250W it will still draw the same amount of power required to run if it was using 600W. The reason is whats not used no the PC side is wasted on Heat and EMF (Electromagnetic Field).
So if your PC is not using all the PSU most of it is lost to this EMF the less power you use the bigger this emf is, however if your consumption is increased part of the EMF is pulled back into the system so to say and used.
And thats where i stop on that part i will have to wait until i return to TAFE.. LOL
But there is no ways a PS3 uses the same amount as 5 fridges as it only has a 200W PSU. A standard fridge uses 350W-400W last time i checked my fridge and thats on 24/7.