A typical enterprise data centre runs at a Power Usage Effectiveness of between 2 and 2.5. The PUE is the ratio between the total power for the facility and the amount of power that actually goes into powering the servers . A PUE of 2 means that means that for every watt that goes into powering the servers and other IT equipment, an extra watt goes into powering other things - cooling, lighting, backup power , etc. A 500W server in a typical data centre is actually drawing between 1000 and 1500W once you take into account all infrastructure needed to keep that server running.
With the number of data centres increasing every day, it is encouraging to see a newer breed of data centre being designed with much lower PUE figures. Google and Microsoft have new data centres with PUE figures of 1.5. A 500W server in that centre is only drawing 750W accounting for infrastructure. That's a big saving. The winner though is Facebook whose brand new data centre has a PUE of a staggering 1.07. That same 500W server in Facebook's data centre is only drawing 535W. Scale that up to hundreds of servers and the power savings are huge. What's more, Facebook have published the specs of the new centre under the Open Compute Project (http://opencompute.org/) so others can do the same. How does your data centre compare?