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 (NASDAQ:SPWR) and Canadian Solar (NASDAQ:CSIQ) 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 (NASDAQ:FSLR) struggles. Motley Fool contributor Travis Hoium covers the trends that investors should look for in the video below.