The reporting of Power Usage Effectiveness (PUE) has been a hot button issue in the industry for some time. PUE has become established as the leading "green data center" metric, but its value has become fuzzy due to a disconnect between companies' desire to market their energy efficiency and the industry's historic caution about disclosure. As a result, there have been many public reports of low PUE numbers that have generated skepticism.
Mike Manos of Digital Realty discussed this trend in a recent post at Loose Bolts about the current problems with PUE reporting. "PUE is poised to be a victim of its own success, in my opinion, unless the industry takes steps to standardizes its use in marketing material and how it is talked about," Mike writes. "These days, I view each and every public statement of PUE with a full heaping shovel-full of skepticism regardless of company or perceived leadership position."
Manos also reports a worrisome sign: a recent data center RFP from a regional government entity stipulating that the facility must have a PUE of 1.2 or lower, a level of efficiency achieved by a handful of working data centers at some of the largest operators. These kind of stipulations represent the sort of misuse of PUE that critics - most notably Ken Brill of the Uptime Institute - have warned about. Brill's concern has been that executives yearning for low PUE numbers would set unreasonable expectations for data center managers.
Manos proposes a solution: "Lets re-claim PUE and Metrics from the Marketing People," he writes. Mike writes at length about the challenges of PUE reporting and possible solutions, including four different types of PUE ratings that he believes can provide common reporting standards and address concerns about apples vs. oranges comparisons. There's no shortage of either detail or opinion in the lengthy post, which is worth reading if you're interested in PUE.
Manos isn't alone in suggesting additional data and/or refinements to PUE. The Green Grid, which popularized the PUE metric, has outlined three tiers of PUE metrics while Amazon's James Hamilton has offered an enhanced standard called tPUE. The government may also have a seat at the table, as the U.S. Environmental Protection Agency has indicated that it will use PUE as the basis for its Energy Star for Data Centers ratings.
How will this play out? Manos cites the need for "an honest, open and frank conversation around this topic." It remains to be seen whether the industry can come together on an approach that addresses the current concerns without undermining the usefulness of the metric for audiences beyond the walls of the data center. It's worth remembering that one motivation in advancing PUE was to simplify discussions of energy efficiency, a goal that could become more elusive if the standard becomes increasingly complex.