2 posts Google's The Case for Energy-Proportional Computing
Energy-proportional designs would enable large energy savings in servers, potentially doubling their efficiency in real-life use. Achieving energy proportionality will require significant improvements in the energy usage profile of every system component, particularly the memory and disk subsystems.
I'm watching with mixed emotions as more and more vendors start to describe their products as addressing challenges associated with reducing power and cooling in the data center. On one hand, clearly it's a monumental challenge -- and opportunity. On the other hand, I'm starting to see vendors with thinner and thinner claims start to add this message to their marketing drumbeat. That's not a good thing.
point out the challenges coming in determing energy efficiency, and you will need to measure the results.
The answer can be relatively simple. Add Power and Cooling measurements to your performance labs capabilitise and RFPs. Some people are adding Green requirements to RFPs, but Green is not a well enough defined area. Instead ask for the true power consumption under max load and idle for the configuration delivered. This should be a # that is relatively easy for your performance labs to verify when measuring the power draw from IT HW.