Moreover, PUE 2 includes more details on how to properly measure and calculate PUE for data centers located in a mixed-use building; in particular, a building supplied with chilled water or condenser water.
One of the significant changes in PUE 2, which may be easy to overlook, is the following caveat regarding the requirement to reference the PUE category when proclaiming a data center's efficiency:
When publishing PUE, the category must clearly be indicated using a subscript e.g. PUE0, PUE1, PUE2, PUE3. A PUE reported without the subscript is not considered to be in compliance with these recommendations.
Table 3: Mapping of PUE categories to TGG framework
PUE category TGG annotation
PUE3 PUEL3, YC
It would seem that very few (if any) of those who have previously made public proclamations of their PUE results have indicated which PUE category methodology and protocols they used to derive their claimed results. Presumably, going forward they will hopefully include the category in future PUE announcements. It should be interesting to see how many organizations adhere to this requirement in any new crop of PUE announcements.
It should be noted that the PUE Version 2 document also states:
The U.S. DOE's DC Pro tool will be incorporating PUE calculations that are consistent with PUE2
The U.S. EPA Energy Star Portfolio Manager tool will be incorporating PUE calculations that are consistent with PUE1.
Going a step beyond the basic information provided by The Green Grid, here are various additional insights and comments from some of the task force organizations.
The Green Grid
From Mark Monroe, executive director of The Green Grid:
When you look at the organizations involved, it's truly amazing the level of agreement and collaboration we have on the future of efficiency metrics. The new definitions help to insure the consistency, transparency, and clarity to the reporting of data center energy use, and help to move the industry to the next level in terms of progressively better measurement capabilities.
U.S. Department of Energy - Save Energy Now
Paul Scheihing, DOE Industrial Technologies Program, Office of Energy Efficiency and Renewable Energy stated:
DOE and EPA worked together to unite key data center organizations to develop these PUE metric recommendations.
The DOE considers the PUE metrics as important and has thus integrated them into our DC Pro tool and Data Center Energy Practitioner training.