Gov. Linda Lingle signed a bill into law Thursday requiring the energy-saving systems in homes starting in 2010.

Hawaii governor Linda Lingle signed a bill into law June 26 that requires the installation of solar water heating systems in homes starting in 2010. "This solar power legislation is another important step in our long-term plan for energy independence in Hawaii," she said.

The Associated Press reports that Hawaii relies on imported fossil fuels more than any other state. About 90 percent of its energy sources come from foreign countries, according to state data.

The new law prohibits issuing building permits for single-family homes that do not have solar water heaters. Some exceptions will be allowed, such as forested areas where there are low amounts of sunshine.

State Sen. Gary Hooser, vice chairman of the Energy and Environment Committee, first introduced the measure five years ago when he said a barrel of oil cost just $40. Since then, the cost of oil has more than tripled. Hooser (D-Kauai-Niihau) stated both the environment and the economy will benefit.

"I'm hoping this will start a trend nationwide," Hooser told the AP. He plans to meet with lawmakers in other “sunshine states,” such as California, Nevada, New Mexico and Arizona, to push similar laws.

Opponents of the law have argued that the mandate is unfair and will drive up home prices in the islands, where a modest home can start at $600,000.

Hawaiian Electric Co. estimates about 85,000 households, or roughly 20 percent of all homes in the islands, already have solar water heating systems. They come standard in many new homes being built by developers.