How Does PUE Effect the Green Effort?
September 03, 2009
Ian Seaton, CPI’s Technical Applications Development Manager, recently answered the following question.
Question: We are currently calculating PUE on a monthly basis and I am looking for ways to make the information more meaningful to others in IT. What type of metrics are you using to show how PUE effects the green effort?
Answer: Power Usage Effectiveness (PUE) is useful as a benchmark for making comparisons between different facilities or comparisons to your own data center over time. So you can either chart your own PUE improvement process or you can use PUE to benchmark yourself against some standard. That will depend on your purposes, but a fairly defensible target is the EPA report to Congress that pegged the average data center in the U.S. with a PUE around 2.0. Then, you might look at how to make that comparison a little more meaningful to more people.
For example, I read somewhere that the average U.S. electrical company produces about 2.095 pounds of CO2 emission for every kW of electricity produced. So let’s say your PUE is 1.6 and your total power load is a half megawatt, so your annual energy consumption might be around 4,380,000 kWh, or 9,176,100 pounds of CO2 pollution – sounds bad, but that is still around 2.3 million pounds less than that hypothetical 2.0 PUE data center, so you can pat yourself on the back for reducing the equivalent carbon footprint of 388 round trip commercial airline flights between San Francisco and New York or heating 488 average American homes for a year. Or, conversely, you can use it as a hammer (carrot?) if you’re trying to drive a team to some PUE target. Several online carbon footprint calculators allow you to calculate your carbon footprint.
If you are interested to see how various data center cooling strategies can affect your PUE, take a look at CPI’s PUE Calculator. For additional help please leave a comment or call us at 800-834-4969. Ian Seaton, CPI’s Technical Applications Development Manager