Darling of the press, renewable energy (RE) is a complex and evolving market with four primary technology sectors—solar, wind, biofuels and fuel cells. In terms of investing in these up-and-coming technologies, Packaged Facts sees the U.S. RE investment market continuing its healthy growth from an anemic $7.5 billion investment value in 2005 to reach $50.5 billion by 2011

Most investors in the U.S. RE market are VC firms. As of end-2007, Packaged Facts estimated that there are at least 100 VC firms active in U.S. RE funding—up from approximately 50 in 2003. Newer to the game, private equity firms are commercializing company funding and project finance—especially in wind and biofuels.