Hawaii has become the first state to require solar water heaters in new homes. The bill was signed into law by Governor Linda Lingle, a Republican. It requires the energy-saving systems in homes starting in 2010. It prohibits issuing building permits for single-family homes that do not have solar water heaters. Hawaii relies on imported fossil fuels more than any other state, with about 90 percent of its energy sources coming from foreign countries, according to state data.

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