Despite critics who insist it can't scale, solar energy has been climbing the "wall of worry" this entire decade, and that effort is showing results. During 2014, 6.3 GWatts of solar power was installed in the U.S., 32% of all new generating capacity. Solar has not displaced natural gas as the "fuel of choice," and California still dominates the industry, with more than half the market, but the sector now employees over 173,000 people and that number continues to grow. The boom has shaken-out into four solid companies worth considering as investments. Read more