Its very nice to answer this thread, i am basically an environmental engineering by profession, done research on climate change and global warming, still working on the energy consumption of educational instituions and data centers in India.
The actual concept of going green literally means " reducing the carbon foot print of data centers of the data centers which are the heart of any business who need online presence" In the recent years there was a sudden surge in number of internet users, thereby increasing the number of data centers supporting them
Prior to this the methodology the data centers are operating consumed heavy power, thats where the actual focus is given, this days the energy consumption is increasing the operating cost, no data center actual want to support environment but willing to reduce their energy bills so promoting them as energy saving DC.
The truth is the method they are adopting to reduce energy consumption this days will be fruitfull only after 6-10 years of running, for an example green servers, green buildings, low AC usage by proper ventillation, high quality servers which consumes lower power, proper planning while constructing the DC will save enrgy
One small ex, consider two processors if one is built in 90nm technology and other is built in 65nm technology the 65 nm technology processor obviously consumes less energy, also a typical Desktop CPU consumes anywhere in the range of 140 -160 watts then you think about the power consumption of one server.
Mainly green DC runs on low power consuming servers, low power consuming networking systems, increasing the number of blade servers etc.
There are lot of research going on in this area, one of my friend from bangalore works for Intel research center here in this processor power consumption stated that soon there will be processors consuming 50% of the current power usage