The Office of Energy Projects Energy Infrastructure Update for December 2017 [pdf] shows that solar and wind generation are growing fast in the US. Comparing to the December 2016 report, total extra capacity was 4.9 GW, or just 0.4% up on 2016, but solar and wind added 12 GW total. Natural gas added another 6.5 GW. Coal dropped by 14 GW (almost 5% of its 2016 capacity).
While the capacity additions for wind and solar are pretty similar in terms of GW added, the growth rates for each are very different with solar adding over 25% of its 2016 capacity in the year compared to 7% growth for wind. Looking at the projected numbers for 2021 in the report, solar is expected to grow by another 150%, wind will almost double. In comparison, natural gas only grows by around 16% and coal sheds another 7% of its current capacity. By 2021, non-hydro renewables will account for more of the US generation capacity than coal, though still far below natural gas.