In my last column I discussed the proposed ASHRAE 90.4 Data Center Energy Efficiency standard. At the time the article published, the second revision for comment (September 2015) mandated a PUE ranging from 1.3 to 1.6, dependent on its location in the 18 geographic zones. Needless to say, the data center industry was perturbed by the implications of a mandatory PUE as part of building standards. Since then, the third revision for public comment was released January 29, 2016. It completely removed all references to PUE, presumably in response to public criticism and comments from major colocation providers as well as hyper-scale cloud and internet heavyweights. The third revision has other complex energy efficiency compliance requirements in lieu of PUE, but we will have to see what happens next, since 90.4 may have further revisions or become finalized in the near future.
Although the 90.4 committee removed the PUE metric in March, the White House announced that under the new data center optimization initiative (DCOI), all federal data centers must reduce their PUE to under 1.5 by September 2018 (unless they are already scheduled to be shutdown as part of the Federal Data Center Consolidation Initiative [FDCCI]).