Solar power is becoming more cost effective by the day, and some of the biggest companies in the U.S. are buying into its potential. Wal-Mart (NYSE: WMT), Costco (NASDAQ: COST), and Apple (NASDAQ: AAPL) are now three of the biggest corporate solar installers in the U.S., and they continue to build more solar every year. 

How can investors play this? SolarCity (NASDAQ: SCTY) and SunPower (NASDAQ: SPWR) are the two biggest players in commercial solar, with SolarCity partnering with Wal-Mart and Apple using SunPower's technology. Erin Miller sat down with solar analyst Travis Hoium to learn more about this trend in the solar industry. 

Great stock ideas for the next year
Looking for more great stocks for next year? The Motley Fool's chief investment officer has just hand-picked one such opportunity in our new report: "The Motley Fool's Top Stock for 2014." To find out which stock it is and read our in-depth report, simply click here. It's free!

Erin Miller owns shares of Apple. Fool contributor Travis Hoium manages an account that owns shares of Apple and SunPower and personally owns shares of SunPower and has the following options: long January 2015 $5 calls on SunPower, long January 2015 $7 calls on SunPower, long January 2015 $15 calls on SunPower, long January 2015 $25 calls on SunPower, and long January 2015 $40 calls on SunPower. The Motley Fool recommends Apple, Costco Wholesale, and SolarCity. The Motley Fool owns shares of Apple, Costco Wholesale, and SolarCity. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.