@Jacad: I think I'm not far away to yours: keep in mind, that monitor and WLAN-hub consumes about 60-70W too. Will check PMac allone tomorrow.
Surprising for me is, that OF seems to have no real or efficient powermanagement (compared to OSX or even MorphOS) - did'nt expect that!

Could be, that I have to test another G5 with different OF, because this one goes (in OF console) after 3 minutes allway to full power blowing (thermal calibratioon is OK).

Measuringsystem is calibrated UNITEC EIM-812 performance measuring device (CATII) - should be exact enough.