Wind power is already practical in many places like Denmark, where 17 percent of the electricity comes from wind turbines. The newest turbines, with propellers as wide in diameter as a football field, produce energy at a cost of 4 or 5 cents a kilowatt-hour. Further refinements like lighter rotors could drop the price by another cent or two, making it directly competitive with natural gas.
• source: Renewable Energy • See also XlnkS5F6