Study: Batteries and clean energy will outcompete fossil fuels by 2020 -- ThinkProgress.org:

Energy storage prices are falling rapidly, allowing new combinations of solar, wind, and energy storage to "outcompete" the costs of coal and natural gas plants, according to a new study...
https://thinkprogress.org/study-sees-significant-drop-energy-storage-costs-77b1f2b15c71/