http://www.phoronix.com/scan.php?page=article&item=880&num=1
"While idling, Ubuntu 7.10 was consuming the most power with 41 Watts
while Fedora 8 Test 3 had consumed the least amount of power at 38
Watts. Both Windows XP and Vista were consuming 39 Watts while idling.
As this system was using SiS Real 256 graphics, Compiz Fusion was not
enabled by default for Ubuntu 7.10, yet it had consumed the most power."