30 KWH/rack, sounds a little high for it to be considered green at a first glance doesn't it? If a normal computer uses about 500W and you had 60 computers, then you would have the same amount of power consumption (.500W*60=30,000W). At a rate of 15 cents per KWH, and if the system was running 24/7 for a month, the system would cost about $3,240 in electricity (30KWH*24hours*30days*$0.15).
But I guess containing 256 processors with 9 cores a piece in a rack changes how everything looks as being green. With the somewhat low power consumption for a normal home computer mentioned above, would cost $13,824.00 monthly for 256 computers and most likely could no keep up with the Cell/B.E. processors.
One thing I find strange is how Intel is building these supercomputers with the IBM based processor technology, and how IBM has decided to abandon the Cell architecture.