Facebook's Prineville data center has a sophisticated cooling system that allows it to conserve water.
The cornerstone statistic — water usage effectiveness, or WUE — came in at .22 liters per kilowatt hour for the second quarter of 2012.
Water usage effectiveness is a fairly new measure for data center efficiency — The Green Grid consortium of green data center experts published a paper on it last Spring. Facebook, which is committing to publishing its WUE on a quarterly basis, may be the first company to release the stat to the public.
Read more at Sustainable Business Oregon.