What will it take to get you to install solar panels on your roof? Lyndon Rive, solar's master salesman, wants to know. Thanks to an innovative leasing program, among other sales enticements, SolarCity has become the largest residential solar installer in the United States. The company, which is based in Foster City, CA, has installed more than 8,000 solar systems since 2006. It tripled in size this year, and Rive, its CEO and cofounder, expects it to double next year.

To reduce the high up-front costs for customers, Rive will lease homeowners the panels at a rate based on the size of their system. As the panels produce power, surplus electricity is sold to the local utility, and Rive says that those sales, combined with the savings from using less power from the grid, will typically reduce the homeowner's electric bill by more than enough to offset the lease payments. He has hired a team to create software that can manage hundreds of thousands of solar projects in 1,000 jurisdictions, each with its own particular requirements. By saving "pennies here and pennies there," he says, and increasing the volume of installations, Rive is driving down the costs of solar power. His hope is that solar will be able to survive without government subsidies in six to eight years. --Kevin Bullis