Say "energy company" to most people, and an oil giant such as ExxonMobil (XOM) or their local utility probably comes to mind. But in an explosion of innovation not unlike the dawn of the info-tech age, the green era is giving birth to a broad and bewildering array of new companies with big ambitions. If fact, many promising clean-energy startups are hitting the market with products and services that could radically alter how we think of, and consume, power.
All of this activity, of course, is in the thick of the worst U.S. recession in decades. That's because these adolescent companies are beneficiaries of the $96 billion in venture and private equity funding that gushed into green technology from 2002 through 2008, according to New Energy Finance. BusinessWeek and GreenBiz.com, a green business information service, teamed up to pick 25 of the most intriguing up-and-coming U.S. energy companies that you probably haven't heard of—yet. Our criteria: These picks are starting to gain traction with real, innovative products and services for sale, they are not yet publicly listed, they are not yet household names, and all have bona fide venture capital backing and other high-profile investors.