Jonathan Koomey: The value of one watt of savings from more efficient IT equipment in a data center

InsightaaS: Many longer-time readers are aware that in addition to the material published on this site, the team publishes in other venues – including as the Sustainable IT columnists for Bloomberg BNA. In our research, consulting and publishing on sustainable IT, we have frequently relied on the insightful work of Jonathan Koomey, Consulting Professor at Stanford University, to understand issues in and implications of energy usage in the data centre.

A recent post in Koomey’s blog provides an excellent illustration of his work: the thoroughness of his research, and the deft way in which he translates abstract issues (here, a one watt savings in infrastructure power draw) with practical management applications (an understanding of the infrastructure cost implications of that watt). The 

In a white paper I wrote for Samsung last fall (Koomey 2012), I analyze the economics of purchasing green DRAM for servers.  Assessing the economics of efficiency improvements in IT equipment requires knowledge not just of energy prices and energy savings, but also of the avoided infrastructure costs associated with lower power computing.

For new facilities, this is a real avoided cost, but for existing facilities that are capacity constrained it’s an opportunity cost—electricity that powers unnecessarily electricity-intensive DRAM chips could have been used instead to power another server that generates useful work.  It’s only in facilities that are not capacity constrained (which are the vast minority, based on anecdotal evidence) where this opportunity cost is not relevant.  There are large variations in those infrastructure costs depending on reliability requirements and type of data center, but it’s still important to understand the rough orders of magnitude for analyzing the economics of improving the energy efficiency of computing equipment in those facilities.

I summarize the results from these calculations in the following graph.  The key result is that avoided infrastructure savings represent more than half of the economic savings associated with reducing computing electricity use in the data center…

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