Hey Andrew
OK lets firstly make sure you are referring to the correct hardware!
G5 PowerPC (or PPC) Macs are no longer made
Intel
MacPros use the
Xeon Chipset with the latest Mac using the
Nehalem version of the Xeon.
To answer your question is difficult because they draw power based on the configuration of the individual Mac. Extra memory, hard disks, RAID cards, Video cards, Monitor(s) or a higher power GFX card will all add to the equation.
So, you go to the local electrical store (or online) and buy a power meter for a few dollars ($20-$40) and run the Mac with the configuration you have and the meter will tell you exactly how much you need in any situation that you test.
Either of these should work:
[
www.p3international.com]
[
www.p3international.com]
Search Google for a good deal.
For instant answers to more than one hundred common FCP questions, check out the LAFCPUG FAQ Wiki here : [www.lafcpug.org]