Solar stocks were plummeting as President Donald Trump’s tax-and-spending bill narrowly passed in the House of Representatives early Thursday, threatening the huge tax benefits granted to clean-energy companies during the Biden-era.

First Solar and Enphase Energy were the worst performers in the S&P 500 index in morning trading, down 5.3% and 18%, respectively, while shares of smaller peer SunRun plunged 41.9%. 

Clean-energy producers like solar companies have worried that the Trump administration will cut back or completely overhaul tax credits introduced by former President Biden’s Inflation Reduction Act from 2022. Those credits can be of up to 50% of a project’s value.

Trump’s bill now moves to the Senate.

“[The] latest draft represents among the most restrictive interpretations we have heard speculated and the closest to ‘complete’ gutting of [the] bill we’ve ever seen,” Jefferies analyst Julien Dumoulin-Smith wrote early Thursday. Questions lingers if the Senate will pass a more lenient version, he added. 

Many solar stocks were struggling even before Trump returned to the White House, dragged down by weak demand for residential solar amid high borrowing costs.

BMO analyst Ameet Thakkar downgraded SunRun stock to Underperform from Market Perform Thursday, cutting the price target to $4 from $9 on the prospects of the tax bill passing and thereby potentially removing the company’s ability to claim the tax credits.

Coming into Thursday trading, SunRun stock had already fallen 11% in the last 12 months. First Solar stock has lost 35% over the same period while Enphase has plunged 60%.