As pointed out in previous blogs, the power purchase agreement (PPA) for wind in 2013 and 2014 were close to 2.5 cents per kWh for 20 years. Can buyers get cheaper electricity for such long term? Wind farm owners do get another 2.3 cents for 10 years in the form of production tax credits (PTC) from the federal government.
Now lets consider solar, for details see this article:
Austin Energy signed agreement to buy solar for less than 4 cents per kWh. Other deals have been signed for lower price.
A similar trend is occuring outside the US, in June 2015 UAE signed an agreement to buy 200 MWp of solar power for 5.84 US cents per kWh.
So, forget regulations and government mandates, economics is driving growth in wind and solar. As mentioned in a blog before, in 2015 wind, gas and solar were the top three sources of new generation (total of 96%), and coal and oil came in at less than 1%.