When the Empire State Realty Trust (NYSE:ESRT) went public in October, its flagship property, the iconic Empire State Building, was one of the most energy efficient buildings in the country. The landmark's retrofit has an Energy Star rating of 80, putting it in the top 20% of all U.S. buildings measured on that scale, as well as a LEED Gold rating for existing buildings. The company behind the transformation at "The World's Most Famous Office Building" is Johnson Controls (NYSE:JCI), one of our favorite energy stocks of 2013. 

In this video, Fool.com contributor Aimee Duffy discusses how Johnson Controls, once a company known solely for its automotive business, is making waves in the energy world. 

Fool contributor Aimee Duffy has no position in any stocks mentioned. Fool contributor Tyler Crowe has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. 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.