The Solar Energy Industries Association said Wednesday that implementing tariffs on panels and cells from Malaysia, Vietnam and Thailand, which account for 80% of the U.S.’ panel imports, would have a “catastrophic impact” on the industry.

In a letter to Commerce Secretary Gina Raimondo, more than 190 U.S. solar companies urged the Department of Commerce not to initiate a trade investigation.

Wednesday’s letter comes after several companies filed an anonymous petition with the Department of Commerce in August alleging that China-based solar cell and module manufacturers are avoiding U.S. tariffs by moving production out of the country. The Department is expected to decide by the end of the month whether to open an investigation.

“The massive duties called for in these petitions, ranging from 50% to as high as 250%, are already having an adverse impact on the U.S. solar industry and, if implemented, would devastate the industry and each of our individual companies,” the letter said.

SEIA estimates that should the proposed tariffs go into effect, it would cost the industry 18 gigawatts of solar deployment by 2023, which is equivalent to all U.S. solar installations prior to 2015. It also represents a sizable chunk of the expected buildout over the next few years. The industry is expected to add 30 GW of solar in 2022 and 33 GW in 2023, according to estimates from energy consultancy Wood Mackenzie.

“We believe the significant uncertainty is a real risk for US utility-scale developers – projects could be pushed out further with increasing disruptions beyond poly [polycrystalline] and freight/logistics,” noted analysts at Bank of America.

The petitioners claim that the bulk of assembly for solar products imported from Malaysia, Vietnam and Thailand actually takes place in China, which is why these goods should be subject to tariffs. SEIA disputes this, saying that substantial work is done outside of China.

“We cannot emphasize enough how damaging these tariffs would be to our companies and the entire American solar industry,” the letter said.

This comes as the industry faces several headwinds, including supply chain disruptions and higher raw material costs.

In June, U.S. Customs and Border Protection issued a Withhold Release Order on silica-based products from Hoshine Silicon Industry due to forced labor concerns in China’s Xinjiang region.

During the second quarter solar costs rose quarter over quarter and year over year across all market segments for the first time since Wood Mackenzie began tracking price data in 2014. Additionally, some key provisions — including an extension of the Investment Tax Credit — were left out of the infrastructure bill. There’s hope within the industry that the $3.5 trillion spending package will include substantial funding for clean energy projects.