"We really ramped up our solar in 2010. Today most of the projects are half or less of the cost now than then." That's not the Sierra Club but Gregory Wolf, the President of Duke Renewables, the subsidiary of Duke Energy. Duke Renewables owns 1,700 megawatts of mostly wind but also solar.
The fundamental reason why solar is booming is the extraordinary and continuing price declines in the industry. Duke reports a 50% price decline in about 2 years. That's a real fact of importance.