Learn from Google how to save electricity while serving millions of request across a globe. Google come up with 5-step approach to build efficient data centers. From the page:
Google's mission is to organize the world's information and make it universally accessible and useful. Hundreds of millions of users access our services through the web, and supporting this traffic requires lots of computers. We strive to offer great internet services while taking our energy use very seriously. That's why, almost a decade ago, we started our efforts to make our computing infrastructure as sustainable as possible. Today we are operating what we believe to be the world's most efficient data centers.
As a result, the energy used per Google search is minimal. In the time it takes to do a Google search, your own personal computer will use more energy than we will use to answer your query.