Uptime CEO: Low PUE Numbers ‘Scientifically Meaningless’

August 26, 2008

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The Power Utilization Effectiveness metric can potentially be useful for determining the gross performance of data center electrical and mechanical systems. However, Kenneth Brill, executive director at Uptime Institute, which developed the concept, warns that PUE claims of 0.9, 1.2 or 1.6 in marketing materials are probably misleading. The typical numbers seen by the Uptime Institute? 2.0 or higher, Forbes reports.

PUE – which is being promoted by the Green Grid – measures the energy going into the data center and the energy delivered to IT equipment, with the difference being “power and cooling overhead.” A PUE of 2.0 means that for every two watts at the meter, only one watt gets to the IT hardware.

Brill writes that PUE claims of 0.9 are “scientifically meaningless, because the marketer making this claim would need to have invented a perpetual motion machine with more energy coming out than coming in.”

Here are some tips Brill recommends:

1. Ask for PUE numbers to be tied to a utility bill and verified by an independent third party to prevent the numbers from being altered.

2. Be aware that electricity is only one of a number of data center energy sources, so some PUE numbers may appear better than they really are.

3. Power is measured at an instant in time, whereas energy is power over time, so a PUE of 1.2 or 1.6 might be accurate but only true at a very carefully selected instant in time.

4. Benchmarking is useful only if you are comparing yourself with others with similar power and cooling equipment types, percentages of load utilization, tier design levels and ZIP codes.

A recent report, developed in part by Uptime, called for an immediate overhaul of corporate management practices and a doubling of the energy efficiency of large-scale corporate computing facilities by 2012.

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Reader Comments

I don’t think that the Uptime Institue developed PUE. The DOE/EPA created the ratio, the Energy Efficiency Ratio (EER) in their August 2007 study. The Green Grid then branded the same ratio as PUE.

Jacque Swartz | January 14th, 2009