A group of eight leading organizations in data center energy efficiency metrics met past January. The meeting involved representatives of the Silicon Valley Leadership Group, the U.S. Department of Energy, The Green Grid, the 7×24 Exchange, The Uptime Institute, the U.S. Green Building Council, the U.S. Environmental Protection Agency’s Energy Star Program, and the HVAC industry group ASHRAE. The outcome of the meeting is an agreement to three guiding principles for measuring energy efficiency in data centers at present:
- Power Usage Effectiveness (PUE) using source energy consumption is the preferred energy efficiency metric for data centers. PUE is a measurement of the total energy of the data center divided by the IT energy consumption.
- When calculating PUE, IT energy consumption should, at a minimum, be measured at the output of the uninterruptible power supply (UPS). However, the industry should progressively improve measurement capabilities over time so that measurement of IT energy consumption directly at the IT load (i.e. servers) becomes the common practice.
- For a dedicated data center, the total energy in the PUE equation will include all energy sources at the point of utility handoff to the data center owner or operator. For a data center in a mixed‐use building, the total energy will be all energy required to operate the data center, similar to a dedicated data center, and should include IT energy, cooling, lighting, and support infrastructure for the data center operations.
According to Julius Neudorfer of North American Access Technologies, in an analysis of the principles:
“This appears to be an effort by these organizations to try to clarify the expected direction of upcoming EPA Energy Star for Data Centers program standards, which is scheduled to be finalized in April. There were some earlier meetings in September and November of 2009 by the EPA working group that were somewhat ambiguous about which metric was going to be used for the certification process and where and how the measurements were going to be taken.”