Google has been at the forefront of energy efficiency quite some time. They recently were written up for their large rooftop solar array. Google has lots of data and metrics to determine the average energy "impact" per search.
Read on to learn more about Google current initiatives.
"
... Data centers ... account for most of Google’s energy needs ... take
our energy use seriously and, from the very beginning, Google has
focused on designing systems that use as little energy as possible ...
operating what we believe to be the world's most efficient data
centers."
" ... Google-designed data centers use about half the
energy of a typical data center ... energy used per Google search is
very small ... currently use about 1kJ (0.0003 kWh) of energy to answer
the average query ... roughly .2g of CO2 ... often take the place of
more carbon- and time-intensive activities, such as driving a car to a
library or spending hours navigating shopping malls."
" ...
commitment to sustainability goes beyond just electricity and carbon
... two Google
facilities currently run on 100% recycled water, and by
2010 we expect recycled water to provide 80% of our total data center
water consumption ... share our own data center best practices and are
encouraging our industry peers to do the same ..."
" ... if all
data centers operated at the same efficiency as ours, the U.S. alone
would save enough electricity to power every household within the city
limits of Atlanta, Los Angeles, Chicago, and Washington, D.C."
Via: Google
LINK