The solar market is back on its feet again after a rough few years dealing with oversupply. The Japanese market is booming and U.S. residential installations are steadily growing. SunPower (SPWR 5.58%) and Canadian Solar (CSIQ 4.48%) have already reported better than expected earnings, while Trina Solar (NYSE: TSL) and Yingli Green Energy (NYSE: YGE) have already raised guidance. But not all solar companies are enjoying the boom, as exemplified by First Solar's (FSLR 1.71%) struggles. Motley Fool contributor Travis Hoium covers the trends that investors should look for in the video below.