A 3-Part Solution to PUE Calculations

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Energy efficiency is always top of mind with data centers operators and is oftentimes a component of business goals. In an article for Data Center Knowledge, I articulated “How to Make Your Data Center PUE Calculation More Accurate.”

The power usage effectiveness (PUE) metric, developed in 2007 by The Green Grid has become the de facto standard for measuring data center infrastructure efficiency. However, there are plenty of examples where PUE measurement falls short of accurate.

To start, there must be agreement on exactly what devices constitute IT loads; what devices constitute physical infrastructure; and what devices should be excluded from the measurement. For instance, various data center subsystems aren’t present in some data centers such as outdoor lighting or the Network Operation Center (NOC).

A common challenge is with subsystems that support a mixed-use facility; they are shared with non-data center functions (for example, cooling towers and chiller plants) so fractions of the power attributable to the data center cannot be directly measured.

Ultimately what we see is commonly published PUE data that is not computed using a standard methodology. So the same data center can have a different energy efficiency rating when different methodologies are applied.

3 Parts

As a data center manager, you will inevitably encounter one or more of these issues when trying to calculate PUE, but using a three-part method will help you define a standard for collecting data and drawing insight from your data center. In turn, you’ll realize how to better calculate PUE.

Part one: Establish a standard for classifying IT loads and physical infrastructure.

Part two: Estimate energy consumption for shared devices.

Part three: Estimate energy consumption for devices that are impractical to measure.
Full details of each of the three parts can be found in White Paper 158, Guidance for Calculation of Efficiency (PUE) in Data Centers. You can also estimate your PUE using this calculator tool.

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