Yeah, wumpus is right. Actually knowing exactly how much power a system is drawing is better than just guessing at it.
Of course even the Kill-a-Watt is only partially useful, since its only measuring what the entire system is drawing at the wall. Even your P4 system isn't actually using 250watts. Your PSU is maybe 75% efficient at best (probably less) so the total system is actually only using 187.5watts peak.
Wumpus I dare you to go post that at Overclockers.com or OCAddiction the next time they say that they need a 500watt PSU.
![Laughing :lol:](./images/smilies/icon_lol.gif)
I hope you're wearing your asbestos undies.
What would be the most useful would be a way as simple as the Kill-a-watt to measure how many amps each component is drawing, and on what voltage line. Your P4 may only be using 180watts, but 160 of that may be on the 3.3 and 5volt lines. That's where an el-cheapo 300PSU wouldn't cut it. But a quality 300W PSU would work just fine.
The problems with sizing PSU's are:
1. You have no real way of knowing what you need.
2. The PSU makers market their product by only the BIG number, which in real use is meaningless.
I think PSU's should be marketed like fertilizer, where instead of listing only the big number, you list the numbers for each of the component lines.
So, for example the 300W Seasonic MikeC just reviewed would be a 92-150-216, while the 400W'er would be a 92-150-264. With the 3 numbers representing the wattage of the 3.3v, 5v, and 12v lines respectively. You break them down that way and suddenly you can see the real differences between the PSU's
(and Ryan200, I rarely do this, but man please learn some punctuation. I had to read your post like three times before it made sense)