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7: The Need for Standard IT Energy-Use Metrics 121

Professional Accreditation

Green building professionals can become LEED-accredited through the
LEED Accredited Professional Exam. This accreditation enables an individ-
ual to facilitate the rating of buildings with the various LEED systems.
Professional accreditation is administered by the Green Building
Certification Institute.
Although LEED is the leading rating system throughout the world for
building energy efficiency, the more-specialized rating system required for
green IT will come from organizations such as the U.S. EPA working with
other government organizations worldwide, professional organizations
(for example, the next section of IEEE’s EPEAT), electric utilities, IT ven-
dors, and so on.

The Green Grid Data Center Power-Efficiency Metrics:
PUE and DCiE

The Green Grid consortium of IT professionals seeks to dramatically raise
ptg
the energy efficiency of data centers through a series of short-term and long-
term best practices and recommendations, which are crucial to the establish-
ment of metric standards. The Green Grid Web site is at http://www.
thegreengrid.org/home.
This section describes the very important energy-efficiency metrics for
data centers produced by The Green Grid. The first white paper published by
The Green Grid in February 2007 was called “Green Grid Metrics:
Describing Data Center Power Efficiency.” In that paper, The Green Grid
proposed the use of Power Usage Effectiveness (PUE) and its reciprocal,
Data Center Efficiency (DCE) metrics, which enable data center operators
to quickly estimate the energy efficiency of its data centers, compare the
results against other data centers, and determine if any energy-efficiency
improvements need to be made. Since then, PUE has received broad adoption
in the industry, but DCE has had limited success due to the misconception of
what data center efficiency really means. A 2008 white paper from The
Green Grid reaffirmed use of PUE, but redefined its reciprocal as data center
infrastructure efficiency (DCiE). This refinement will avoid much of the con-
fusion around DCE and will now be called DCiE.
In the long term, The Green Grid is developing metrics to measure data
center productivity as well as efficiency metrics for all major power-consuming
subsystems in the data center. To promote these metrics and drive greater data
center energy efficiency for organizations around the world, The Green Grid