Technology Review has an article on Google’s (suprisingly low) energy consumption - What It Takes to Power Google.
Google is the first major Web company to reveal exactly how much energy it uses—information that will help researchers and policy makers understand how the massive explosion of Internet usage and cloud computing is contributing to global energy consumption.
Google uses 260 million watts continuously across the globe, the company reported on Wednesday. This is equivalent to the power used by all the homes in Richmond, Virginia, or Irvine, California (around 200,000 homes), and roughly a quarter of the output of a standard nuclear power plant.
By far, the majority of Google's energy use is associated with its data centers, according to Jonathan Koomey, a professor at Stanford University and a researcher who focuses on energy and IT. He says that 80 to 90 percent of those watts are used solely by the company's data centers, based on estimates he made of Google's power use in an August 2011 report. Most of this energy is used in powering the IT equipment in Google's data centers. Google custom builds many data centers, such as a new one in Finland that uses a seawater cooling system, to cut down on electricity costs.
This has enabled Google to be relatively energy efficient, says Koomey, who estimates that the company owns about 3 percent of servers worldwide and uses only 1 percent of electricity for data centers worldwide. "They're operating more efficiently than other data centers," he says.
Other Web giants, including Amazon and Facebook, probably operate their data centers with similar efficiency due to hardware and software customization, and innovative cooling equipment, Koomey says. However, the majority of data center power use comes from non-IT companies running their own data centers less efficiently [which is in turn, far less than that used by equipment in homes and offices].
In its report, Google compares the energy usage of companies' in-house computer systems to the energy used by its cloud servers. It estimates that running Gmail instead of an in-house e-mail system can be almost 80 times more energy efficient. Google says that 25 percent of its energy was supplied by renewable fuels—such as from wind farms—in 2011, and plans to increase that to 30 percent this year.