power supply calculator website. How good?

[hojl]

I found this website to see how much power i need. i was wondering how accurate this website is. If this website is no good can u recommend another site?

http://www.extreme.outervision.com/PSUEngine

 

[Miramonti]

I've always loved this site but it looks high to me. The most I draw is <400w with my system (measuring with a Kilawatt meter) and it recommends 633 watts with a minimum 583w.

 

[hojl]

Thanks.. I was wondering how accurate it is.. I rather it be on the higher side than lower. hehe