Stop beating a dead horse: PUE is not an effective tool to reduce the cost or environmental impact of IT

Matt Stansberry, Director of Content and Publications, Uptime Institute

Senior executives understand the importance of reporting and influencing IT energy efficiency, and yet they are currently using inappropriate tools and metrics for the job. The misguided focus on infrastructure masks, and distracts them from addressing, the real systemic inefficiencies in most enterprise data center organizations.

Power Usage Effectiveness (PUE) is an engineering ratio that data center facilities teams can use to capture baseline data and track the results of efficiency improvements to mechanical and electrical infrastructure. It is also useful for design teams comparing equipment or topology-level solutions. But, as industry adoption of PUE has expanded the metric is increasingly being misused as a methodology to cut costs and prove stewardship of corporate and/or environmental resources.

In 2007, Uptime Institute surveyed its Network members (a user group of large data center owners and operators), and found an average PUE of 2.5. The average PUE improved from 2.50 in 2007 to 1.89 in 2011 in Uptime Institute’s data center industry survey.

So how did the industry make those initial improvements?

A lot of these efforts were simple fixes that prevented bypass airflow, such as ensuring Cold Aisle/Hot Aisle arrangement in data centers, installing blanking panels in racks, and sealing cutouts. Many facilities teams appear to have done what they can to improve existing data center efficiency, short of making huge capital improvements.

From 2011 to today, the average self-reported PUE has only improved from 1.89 to 1.70. The biggest infrastructure efficiency gains happened 5 years ago, and further improvements will require significant investment and effort, with increasingly diminishing returns.

In a 2010 interview, Christian Belady, architect of the PUE metric, said, “The job is never done, but if you focus on improving in one area very long you’ll start to get diminishing returns. You have to be conscious of the cost pie, always be conscious of where the bulk of the costs are.”

But executives are pressuring for more. Further investments in technologies and design approaches may provide negative financial payback and zero improvement of the systemic IT efficiency problems.

Feedback from the Uptime Institute Network (our longstanding data center operations user group) confirms Uptime Institute’s field experience that enterprise IT executives are overly focused on PUE.

According to the Uptime Institute’s Annual Data Center Industry Survey, conducted January-April 2014, the vast majority of IT executives (82%) tracks PUE and reports that metric to their corporate management. By focusing on PUE, IT executives are spending effort and capital for diminishing returns and ignoring the underlying drivers of poor IT efficiency.


For nearly a decade, Uptime Institute has recommended that enterprise IT executives take a holistic approach to significantly reducing the cost and resource consumption of compute infrastructure.

Historically, data center facilities management has driven IT energy efficiency. According to the Uptime Institute’s Annual Data Center Industry Survey (2011-2014), less than 20% of companies report that their IT departments pay the data center power bill, and the vast majority of companies allocate this cost to the facilities or real estate budgets. This lopsided financial arrangement fosters unaccountable IT growth, inaccurate planning, and waste.

The data center design and facilities management communities should be proud of their accomplishments in improving power and cooling infrastructure efficiency, yet the biggest opportunities and savings can only be achieved with an integrated and multi-disciplined IT operations and management team. Any forthcoming gains in efficiency will depend on getting the hardware and software disciplines to take up the mantle of pursuing efficient IT on a holistic basis.

Rising energy, equipment, and construction costs and increased government scrutiny are compelling a mature management model that identifies and rewards improvements to the most glaring IT inefficiencies. At the same time, the primary challenges facing IT organizations are unchanged from almost 10 years ago.

Uptime Institute’s Founder Ken Brill identified the following as the primary culprits of poor IT efficiency as early as 2007:

  • Poor demand and capacity planning within and across functions (business, IT, facilities)
  • Significant failings in asset management (6% average server utilization, 56% facility utilization)
  • Boards, CEOs, and CFOs not holding CIOs accountable for critical data center facilities’ CapEx and data center operational efficiency.

Perhaps the industry was not ready to hear this governance message and the economics did not motivate broad response. Additionally, the furious pace at which data centers were being built distracted from the ongoing cost of IT service delivery. Since then, operational costs have continued to escalate as a result of insufficient attention being paid to the true cost of operations.

But, in order to address any of these systemic problems, companies need to secure a commitment from executive leadership by taking a more activist role than previously assumed.

This kind of cohesion is necessary for a firm to conduct effective cost modeling, implement tools like DCIM, and overcome cultural barriers associated with a new IT efficiency program.

Executive leadership should consider the following when launching a formal IT energy management program:

  • Formal documentation of responsibility, reporting, strategy, and program implementation
  • Cost modeling and reporting on operating expenses, power cost, carbon cost per VM (virtual machine), and chargeback implementation
  • KPIs and targets: power, water, carbon emissions/offsets, hardware utilization, and cost reduction
  • DCIM implementation: dashboard that displays all KPIs and drivers that leadership deems important for managing to business objectives
  • Incentives and recognition for staff.

Uptime Institute will continue to produce research, guidelines, and assessment models to assist the industry in self-governance and continuous improvement. For case studies and further details, please see the research in the Uptime Institute Journal and the Uptime Institute’s Brill Awards for Efficient IT.

Share on FacebookTweet about this on TwitterShare on LinkedIn