Rapidly falling capital costs are a main reason why wind, solar, and gas now dominate the new construction market for power plants. EIA calculates that capital costs for the three are down 10% to 22% since 2010.
The capital costs for a large solar farm and a big wind farm fell 22% and 13% respectively. A conventional natural gas plant saw its costs fall 10%. See Table 2 at page 7.
In the first quarter of 2013, all new electricity generation built in the USA was wind, solar, or gas. Falling capital costs of the Big Three are making each more competitive than ever!