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The data center energy metrics you might be missing

Feb 27, 2014

When discussing green data center energy metrics, the acronym you’ll hear thrown around most often is PUE, or power usage effectiveness. PUE takes into account how much energy the servers (and their associate devices, like lights, coolers and work stations) consume.

A feasible goal for PUE is around 1.75, meaning for every watt of energy used by the servers, .75 watts are used for the peripheral support of the data center. In a perfectly efficient data center (of which there are none yet), the PUE would be 1.0.

Though vitally important, PUE only takes a glimpse at one little part of what’s actually going on in the data center, and sometimes doesn’t even do all that great of a job.

For example, one could manufacture an inaccurately low PUE by having a host of old servers plugged in but not being actively used. Undoubtedly, it would be uneconomical in terms of energy expenditure, but in terms of PUE, those servers would only be using a small percentage of their full energy consumption thanks to being set to standby. This lowers PUE artificially.

To avoid such pitfalls, diversify the way you take measurements of your system with these other types of measurements, helping you create a happy, efficient data center:

Carbon usage effectiveness (CUE)

CUE measures the emissions associated with your data center. Many data specialists are predicting CUE to take PUE’s spot as the premier metric in years to come. CUE doesn’t just track the amount of energy consumed, it also examines the type and source of it. For example, data centers that draw energy from renewable sources are infinitely more efficient and sustainable than those that source from say, a coal plant. CUE can help organizations determine exactly how many carbon offsets they should be utilizing to sustain veritably “green” operations.

Water usage effectiveness (WUE)

Water has been humanity’s most precious resource since the founding of civilization – tracking its competent use alongside electricity should seem natural. WUE can be calculated through evaporative cooling measures. Mathematically, divide the annual water usage for a data center by overall IT equipment energy consumption to derive a WUE value. A word of caution: WUE is sometimes confounded by competing, adjacent HVAC systems that are constantly humidifying and dehumidifying the same air.

Of course, CUE and WUE are just the tip of the iceberg. There are many more metrics that directly relate to building specs (like ASHRAE, data center productivity and Energy Star). It’s important to realize that one way of measurement shouldn’t be your singular “Holy Grail” – the key is using many metrics in tandem to triangulate in on efficiency.

For more information on how sys-tek can help you design and run a green data center, contact us.

You may be interested in these other posts:

• The Hospital Energy Alliance
• Building Energy Efficiency Incentives
• 3 tips for finding a green data center