The Linux server operating system is a better power-saver than Windows Server 2008, according to Computerworld writers Tom Henderson and Rand Dvorak:
Our tests point to Linux as the winner of the green flag by margins that topped out at 12 percent. But we must note that our results are full of stipulations imposed by our test bed, and as the more truthful car advertisements might warn, your wattage may vary.They tested Red Hat Enterprise Linux, SuSE Linux Enterprise and Windows Server 2008, the story says, on servers from IBM, HP and Dell, and on a variety of settings (high efficiency vs. high performance). Windows did prevail in certain tests when its highest "power-saving settings were on," but Red Hat most consistently pulled less power when looking at all the tests together.
Regardless of the server OS, however, the writers point out that "getting your servers to be green" is a tough job because there is a "disconnect" between power-saving mechanisms and the ability for applications to quickly react to system and user requirements.