#1 Aaron Hall

Borrego Solar Systems

Age: 29
Location: El Cajon, CA
2007 Revenue: $30.3 million
Employees: 160
Year founded: 1980
Website: www.borregosolar.com

In 2001, while a senior at Northwestern, Hall wrote a new business plan for this struggling solar power company, as part of an economics class. He later presented it to the company's founder, a family friend. The rest is history. Since then, Borrego -- which installs solar power systems for residential, commercial, and public sector clients -- has grown by more than 1,000 percent, earning the No. 261 spot on 2008 Inc. 5000 list of the nation's fastest-growing private companies. Its 50 solar power installations in New England alone have offset up to 2.4 million pounds of carbon dioxide emissions in the past year, the equivalent of planting 1,000 acres of trees.

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