Simple PSU Question

This is actually a question just out of curiosity. Given a standard name brand (say Antec or Tt) 480watt PSU, does the unit actually eat ~480w out of the main power consistently, or does it fluctuate based on the needs of the rest of the system? ie go up and down while different components are being used.

You may be right about the fluctuation based on need but about the rest I don't think is quite right. As far as I know OEMs rate their units on the power they draw from the socket and efficiency (65~68% not 70%, depending on brand) is what the computer receives. This is why those with low efficiencies like most off-brand PSUs get a bad rap.

Here is an article from a reputable site you can read to get yourself up to speed:
http://www.anandtech.com/showdoc.html?i=1841&p=1

As for PFC, to my understanding (I may be wrong) most PSUs, if not all, have it. It keeps the DC flow clean and consistent (some decrease in output efficiency here). However most units do this through a passive method, but then there are those who use an Active method (APFC) like in some units distributed by Tt or Forton. The active method basically does an even better job at providing a cleaner DC flow but again decreases output efficiency even more by powering the active mechanism.

I think I'm somewhere near the target but someome please correct me if I am wrong, I like to know how things -really- work

Ok, I think this was your question: "If I buy a 480 Watt power supply, is is constantly sucking 480 watts worth of power from the outlet?" Answer: NO. 480 watts is the MAXIMUM that that unit can supply. It will draw enough to power the given components that are running at any given time. So, it does flucuate. When your CD-ROM spins up, it draws more power. When you load up FarCry and turn all your case fans, that draws power. If you just have your comp running idle, it draws less power than when its not. But the part about efficiency is right. Say at a given moment, your system is pulling 210W, and your supply has a .70 efficiency. At that point, your system is actually pulling 300W (because 300 X .70 = 210) from the wall socket. The extra 90W are converted into heat because the supply is not 100% efficient, it loses some of the wattage while it converts outlet power to mobo-acceptable power.

"The only way to overcome temptation is to yield to it" - Oscar Wilde