Yahoo! announced this week that it would build what it said what would be the greenest, most energy-efficient data center in the world, powered by Niagara Falls.

Data centers are some of the heaviest users of electrical power there are, both to run the servers themselves and to cool them. In fact, a typical data center facility spends almost half of its energy consumption on the systems powering and cooling the computers inside, and not on the computers themselves, according to a website on the subject created by Google, itself one of the largest such users.

Indeed, the cost of energy is such a major factor in data center costs that siting them is typically based more on the cost of energy than on anything else.

In addition to using Niagara Falls, the Yahoo! data center will use a building design that takes advantage of Lockport, N.Y.'s microclimate to use 100 percent outside air to cool the servers, said David Filo, whose title is "Chief Yahoo." (And as a former resident of that region, I can confirm that the air is very cooling, particularly in winter, where Buffalo is in western New York's snowbelt due to the "lake effect" from nearby Lake Erie.)

The result, Filo said, is that the data center will have an annualized average PUE (power usage effectiveness) of 1.1 or better.

In comparison, Google said in October 2008 that it is averaging a PUE rating of 1.21 across its six company-built data centers, and one of its facilities is operating with a PUE of 1.13, the lowest ever published and just above the “perfect” efficiency score of 1.0.