Does Green IT Really Impact Bottom Line Green?

Articles like this one from BusinessWeek are abound. Big dollars are to be saved by by going green in the datacenter and every company's operations group should be taking a careful look at their own usage.

I'm generally suspicious of this kind of math because I've used it myself. Nice, careful selection of numbers and wham-o... big dollar savings that are hard to ignore. Wes Wasson referred to these kinds of numbers as a "BHAC" - Big Hairy Audacious Claim. The irony, he once noted, was that the more extravagant they get, the less they get questioned. To his credit, Wes stuck to numbers he could back up but being a good marketeer, he was quick to identify gems when he saw them.

I did some recent work with respect to power savings in networking and I have to say that a lot of the claims aren't nearly as outrageous as they initially sound. In one particular analysis, I calculated that saving 6W of power per blade in a fully populated 49U rack (the tallest rack that APC makes) across a 10,000 sq. ft. datacenter full of 7Ux16 blade servers in San Francisco saved $750k/yr in power and cooling costs assuming 35% rack density. Granted, it's unlikely a 10,000 sq. ft. datacenter is only going to house blade servers and nothing else, but given that the typical rack can consume upwards of 20-30kW, the fact that shredding 672W per rack (2.24% of a 30kW rack) can generate such a significant savings surprised even me.

Now consider that most datacenters are 20-30k sq. ft. and many new datacenters are 100k sq. ft. and you can start getting a sense of what kind of impact a mere 5% power savings can have on the bottom line.