The decline in the cost of wind power has been impressive over the past few decades, and it's continuing. As this graphic by the American Wind Energy Association demonstrates. the cost of wind power in the U.S. has fallen from around 55 cents per kilowatthour in 1980 to less than 10 cents per kilowatthour today. The result is that wind power is rapidly becoming cost competitive with natural gas-fired electricity.
The Visualising the Production Tax Credit for Wind Energy study by the University of California and Syracuse University shows wind costing only $0.0035/kWh more than gas when levelised over the 20-year life of a typical wind project.
This is the result of taking into account the cost of the environmental impact of gas power stations, as well as the predicted volatility of wholesale gas prices...
... adding in the other factors finds an adjusted levelised cost of electricity for wind of 0.092/kWh, versus 0.0885/kWh for gas.