Solar Panel Tariff May Further Strain U.S.-China Trade

But before starting what could be lengthy litigation, the safest strategy for each importer, according to trade lawyers, is to pay immediately the duties and accrued penalties for shipments received since January, and to start paying the duty going forward.

“We’re taking this very seriously — it has a large financial impact in the United States and it has global ramifications,” Mr. Resch said.

Top officials at Customs and Border Protection, the agency that succeeded the Customs Service, could overrule the technical specialists who determined that the sophisticated panels should be treated like electric generators. Such a move would extend duty-free treatment to the latest solar panels. But that would mainly benefit Chinese producers, whose share of the market has surged in the last two years.

It would also reduce the incentive for companies to manufacture panels in the United States — a politically touchy decision at a time when American cities have been vying for panel factories even as the industry is shifting production to China.

Importers, a mixture of foreign and American manufacturers and distributors, are liable for duties and penalties, not consumers who bought imported panels in recent years.

Imports account for almost half of the solar panels sold in the United States.

Customs issued its ruling on Jan. 9, less than two weeks before President Obama took office. The ruling said that a panel from Trina Solar of China was really a generator because it was equipped with a diode that allows electric current to pass around areas of the panel that are shaded. The diodes have become standard on solar panels, and are effectively required to meet American safety standards.

Javier Muniz, the chief executive of GES USA, said through a spokeswoman that GES solicited the customs opinion last winter for a project that did not end up being built. GES did not tell other companies about the ruling, he added.

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Even Trina Solar, the Chinese panel maker, became aware of the decision only “in recent weeks,” a Trina spokesman said. Industry leaders have stayed very quiet about the customs decision in the last few weeks while holding emergency meetings to decide on a legal strategy.

Unlike many large overseas manufacturers, Trina still exports directly from China to independent distributors in the United States. Trina does not have a American subsidiary to import the panels and handle the customs paperwork.

“Trina Solar is currently classified as an exporter and is not liable for the duty arising from these regulations,” said Terry Wang, the company’s chief financial officer.

Suntech said that it was aware of the customs decision and was looking into it.

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Mr. Resch estimated that the duty would cost the industry $70 million this year, and there would be more tariffs in the years to come.

That calculation assumes the industry will be found negligent for not paying the duty on panels imported since January and will be assessed the doubled duty. It assumes the industry will not be found liable for shipments in the preceding five years.