The U.S. imports most of its solar panels. A new ruling may make that more expensive

Workers install solar panels on a rooftop at AltaSea's research and development facility at the Port of Los Angeles on April 21, 2023. (Mario Tama/Getty Images)

The Department of Commerce has determined that solar panel manufacturers in four Southeast Asian countries are evading U.S. trade rules by using Chinese-sourced materials subject to tariffs without paying applicable duties. Those countries — Vietnam, Malaysia, Thailand, and Cambodia — are responsible for nearly three-quarters of solar modules imported to the United States.

The ruling, unveiled Friday, means that new U.S. solar projects may soon be more expensive: manufacturers whose goods run afoul of Obama-era solar tariffs will be subject to additional import duties on their products.