For this green IT benchmark, being a zero is a good thing

Data center managers with a green bent need to bone up on the first of two new metrics being rolled out by the Green Grid, the industry association that has been pushing the whole power usage effectiveness (PUE) thing when it comes to the efficient operations of data centers.

As been reported here on ZDNet, the organization has introduced a new measure of data center energy efficiency and sustainability called carbon usage effectiveness (CUE). (There's another metric coming next year called the water usage effectiveness ratio, but it's not out yet so I'll pick that up at a later date.) I got curious about the differences between PUE and CUE, so I just read the white paper that talks about how to calculate the new CUE measure and why it's a useful thing to monitor.

First, here's a quick definition of both PUE and CUE:

• PUE = A measure of the infrastructure energy efficiency that looks at the all the energy needed to run a data center to its optimal capabilities versus electricity devoted strictly to the IT inside it. Meaning, the electricity for the cooling systems and lights, vs. the electricity for the servers and such. An ideal ratio is "1."
• CUE = This focuses on the carbon impact of a given data center. The ideal value here is "0," implying that there are no carbon emissions associated with a given site.

(The WUE, which you'll hear more about come March 2011 will determine the ration between the amount of water delivered to a facility and the amount of water that goes into actually delivering IT "work.")

CUE is measured by dividing the total carbon emissions caused by data center energy by the amount of energy used by the IT equipment in your data center. Actually, there are three different potential calculations, according to the white paper. The Green Grid suggests actually using carbon emissions that gather real-time information from whatever the local power source might be and convert it into data specific to your facility. Barring that, it suggests making educated guess-timates based on the technical specifications of the equipment you're measuring.

Why should you even care about this or look at CUE?

According to the Green Grid, measuring CUE will provide you with a way of improving your data center sustainability message, a more direct measure of the carbon associated with the main hub of your IT operation. You should care because this will help you include this metric when you're evaluating your data center against similar ones OR when you're trying to determine all of the relevant variables when switching from an onsite data center operation to one that is potentially hosted in the cloud.

One of my "predictions" for 2011 is that discussions about the cloud will increasingly consider the energy consumption metrics around an evaluation. Carbon will be a secondary part of that, especially as more businesses move to continue reducing both their absolute emissions and their emissions per revenue dollar. You should definitely read up on this new metric. The Green Grid is planning a whole series of white papers, including how to measure CUE for mixed-use buildings (probably most of you reading this) and how to calculate CUE for sites generating their own energy.