Houston, the undisputed fossil fuel capital of the United States, has made an interesting discovery that doesn't involve dead dinosaurs: it's cheaper to buy wind power. Beginning this week, the nation's fourth largest city has started using wind-powered electricity for about 25 percent of its municipal power needs. The power comes from west Texas wind farms at a negotiated rate of 7.5 cents per kilowatt hour. That's two cents per kWh cheaper than buying electricity from the conventional power grid.

City officials say this weeks move was prompted in part by the infamous 2005 hurricane season. Hurricane Katrina in particular caused major damage to oil and gas infrastructure. That in turn increased the price of natural gas, which Houston relies on heavily for electricity. The city expects to use as much as 1.7 billion kWh of wind power over the course of the five-year contract.

Even more surprising about this week's news is that it represents a trend, not a one-time anomaly. According to the EPA's Green Power Partnership, Houston is the top municipal purchaser of green power in the nation.

"We begin taking this wind power today as a benefit for both the environment and the taxpayer,” Houston Mayor Bill White said on Tuesday. "As the energy capital of the world, Houston is committed to becoming the clean, sustainable energy capital of the world as well."