Dumbfounded by how much energy is consumed by a dual-G5 PowerMac, I've decided to do everything I can to reduce its energy consumption.
Some folks have converted their G5 cases to x86:
http://www.halfzware.com/wordpress/2006/01/16/selling-my-powermac-g5-case/
http://www.overclockers.com/tips1133/index02.asp
http://forum.insanelymac.com/lofiversion/index.php/t4525.html - scroll down for pics
http://www2.arnes.si/~mbabic/G5%20x86%20project/
I definitely do not want to do that! Instead, I'll just do everything I can to make sure the machine is lean as can be. Here are a couple initial ideas:
The dual-G5 does use a lot of energy: about 144 watts at idle, with no display. Add a display or two and you're up over 200. That's with one graphics card, (4) 512MB ram chips, 1 sata drive, and a mouse and keyboard. Also, I set the processor to "reduced" performance. The "spin down hard disks when possible" option didn't seem to do much. Putting the computer to sleep reduced its power consumption to about 5 watts. Dual G4 Powermac
I was glad to find that the Dual-G4 fares better - though its obviously slower. Mine runs at about 80 watts without a display or any usb peripherals. With some tweaking, I might be able to get that lower. Titanium Powerbook - a.k.a. Tibook
The Tibook has great efficiency. Mine runs at about 18 watts idle with the display dimmed, but still visible. I was surprised it was so low. What's nice is that you can also run the TiBook with the lid closed, using an external display and peripherals. Mac Mini Power
http://docs.info.apple.com/article.html?artnum=304952 - much better!iMac Power Consumption
http://www.silentpcreview.com/article693-page1.html
http://weblog.infoworld.com/enterprisemac/archives/2006/02/imac_keeps_its.html
http://www.girr.org/mac_stuff/intel_imac_tips.html
I just bought a iMac 17" for my office - and I'm very glad I did. Its a fast machine and as you can see from the links above, very energy efficient. I'm surprised though that the Mac Pro's aren't more energy efficient. Mac Pro Power Consumption
http://docs.info.apple.com/article.html?artnum=304387
http://www.amug.org/amug-web/html/amug/reviews/articles/intel/macpro/
Like making your car more fuel efficient by not driving it - I think the best way to make the dual-G5 more efficient is by not using it. :-(