After a rough couple of years, the solar industry has been an extremely hot segment of the stock market in 2019. First Solar (NASDAQ: FSLR), SunPower (NASDAQ: SPWR), Sunrun (NASDAQ: RUN), and Vivint Solar (NYSE: VSLR) are all up over 40% as of this writing, and Chinese manufacturer JinkoSolar (NYSE: JKS) has nearly doubled.