Two very noteworthy announcements in the past few weeks for those concerned with diagnosing how energy efficient their data centers are. And (surprisingly) these announcement & tools are coming from the US government who, in my opinion, is out in front of industry for the first time.
First, the US DOE is now beta-testing it's "DC-Pro" (Data Center Profiling) tool as part of it's "Save Energy Now" program. The tool is in its beta-testing stage, and is currently available here, with a really complete FAQ available as well. This tool is great in that it asks for tons of information (an education in-and-of itself), yields an anonymous ranking of your data center relative to peers, and also makes suggestions as to where else you can seek additional efficiencies in your environment.
Second, and in conjunction with the DOE, The US EPA is piloting its Energy Star rating for data centers, much the way they have Energy Star ratings for buildings/structures. The EPA is extending initial participants in the study to July 1, 2008. Information, expression-of-interest forms, etc. are available on the EPA Enterprise Server and Data Center Efficiency Page. Cassatt, among others, will be part of this study -- which also ranks efficiencies of data centers and awards the Energy Star label to the top quartile of annual participants. Note that this is less a diagnostic tool (as-is the DOE DC-Pro tool) and more of a recognition of performance.
My suggestion is to participate in both... If for no other reason than it will *cause* your organization to begin to ask questions, take measurements, and begin to learn tactical/tangible sources of efficiency improvements -- rather than simply discuss abstract concepts.