What’s the best measurement of success in an organization when your talking about energy savings? Cash savings is great because it’s quantified in the most important business metric. Unfortunately it does not correct for changes in IT load and utility pricing. kWh gets at what is most controllable by efforts of the group trying to save energy, but again needs to be calibrated for IT loads. If we benchmark against expected energy spend (vice previous spend or trended spend) then we can use the actual IT load and the results can represent what the energy efforts actually accomplished. PUE doesn’t need any calibration, but it isn’t quantified. The statement PUE went from 1.77 to 1.65 is meaningless to a income statement. And those are the results with impact ( save $400,000 a year with a net present value of $2,500,000 and a first cost of $300,000 for improvement is a great victory to anyone in corporate finance). It’s a juggling act, maybe it depends more on who is seeing it. But when your getting evaluated for year end performance, which is most important?
PUElink - Saving Energy and Maximizing Capacity 
I think it depends on the audience, if you are at a seminar or showing off your results to someone who understands the lingo then PUE is good at a bare minimum. But lets face it, business is about the exhange of goods/services for usually money, and when you can show how you brought more of that money in or saved more money, then everyone can understand.
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King dollar rules all. But my issues is other variences can play into $, such as more IT load, increased utility rates, or unseasonably hot weather. The people making structural changes to save energy still save energy over the base case, but the model doesn’t show the base case correctly.
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I think the people who matter and the people who will appreciate the dollars saved will ask the correct questions to know how it was established. Take “cars” for an example. I tell a group of people it takes me $60 to fill up my tank. Half of the people will just think “thats about what I pay.” Another quarter will ask “well how big is your tank?” Another eighth will ask how often do you drive?” Then the last eight will ask “how many miles can you drive on one tank?” What is the most important question here? Well that depends on what you are trying to figure out, but to give the best estimate on how your money is being spent you need to take in all factors..
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I would agree with Alex in that the audiance is key. Not every question has only one answer.
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Merely reporting PUE reduction does not capture the capex spent to bring the efficiency improvement, e.g. installing VFD fan, better control system etc. Best measurement for success in energy saving should be in dollar value, ROI, NPV etc..
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Great point. I encourage the opportunity to compete on NPV with other projects in the portfolio. We have some of the best investment opportunities on the planet in our centers.
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