A recent report by Worldwatch Institute says solar energy has the biggest global growth rate of all energy sources. One of the biggest solar cell growth areas is meeting power needs of individual households.

Japan leads in rooftop solar programs, which installed solar cells on 9,400 homes last year and plans another 13,800 residential installations this year, the report says. Meanwhile, both the U.S. and the European Union are setting goals to install one million solar rooftop systems by the year 2010.

In the U.S., the local energy service provider is the prime mover in installing solar power. The providers often respond to strong interest from customers who even say they’ll pay just a little bit more on their electric bills in order to receive renewable solar energy. Much of the new investment in solar projects is the result of the Utility Photovoltaic Group’s TEAM-UP program, now with $5 million in cost-sharing funding from the U.S. Department of Energy.