You've no doubt seen the familiar Energy Star label emblazoned on computers, refrigerators, televisions, and other electronics and appliances, indicating that the machine you're using is among the crème de la crème of energy efficiency. In the not-too-distant future, a select group of organizations will be able to proudly display a similar seal on their data center walls. Whether the seal accurately or fairly reflects a high level of energy efficiency, however, remains to be seen.

After many months of crunching data center statistics and working with players from all walks of data center life, the EPA has announced that it will release on June 7 the finalized Energy Star performance rating for data centers in Portfolio Manager, the group's energy management tool for tracking and assessing buildings' energy and water consumption.

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The new rating is based heavily on the popular PUE metric, which compares the amount of energy a data center uses as a whole -- for IT, power delivery, cooling, and so on -- to how much it uses solely for powering IT gear. The lower a PUE rating, the more efficient the facility. According to the EPA, PUE generally ranges from a 1.25 (good) to a 3.0 (not so good).

Rather than being a raw PUE calculation, though, the new Energy Star rating -- ranging in scale from 1 to 100 -- is based on how the data center's actual PUE compares to its predicted PUE. That prediction is calculated based on the facility's annual IT energy use and essentially tells you what the average PUE would be for data centers similar to yours in size and operating characteristics and with the same annual IT energy use.

Achieving the predicted PUE would earn you a rating of 50, meaning your facility has average efficiency for its size, energy use, and IT load. A facility with a score of 75 or higher -- which means it's among the top 25 percent of energy-efficient data centers -- is eligible for the Energy Star.