More than half of America’s nuclear reactors are bleeding cash, racking up losses totaling about $2.9 billion a year, based on a Bloomberg New Energy Finance analysis.

Nuclear power plants are getting paid $20 to $30 a megawatt-hour for their electricity, Nicholas Steckler, an analyst at Bloomberg New Energy Finance, said in a report Wednesday. Meanwhile, it costs them an average of $35 a megawatt-hour to run. That puts 34 of the nation’s 61 plants out of the money, with almost all of the merchant reactors owned by Exelon Corp., Entergy Corp. and FirstEnergy Corp. appearing to be below break-even, he said.

The report underscores the increasing pressure nuclear power generators are facing even as cheap natural gas and renewable resources encroach on their share of the U.S. power market. States including New York and Illinois are now working to subsidize nuclear plants to keep them generating emissions-free electricity.

“It’s a real threat to carbon-emission reductions,” Steckler said by phone Wednesday. “How regulators confront this widespread challenge has massive implications.”

Entergy declined to comment on the profitability of its individual plants but said merchant nuclear generators selling power into wholesale markets are facing “financial challenges due to sustained wholesale power price declines and other unfavorable market conditions.” That’s why the company has shifted focus to the regulated utility business, it said in an emailed statement.

Exelon didn’t immediately have comment. FirstEnergy said it has already “publicly stated that our competitive subsidiaries are not profitable, which includes all of our competitive generating plants” and declined to disclose financial details for its individual generating units. The Akron, Ohio-based utility owner has said it may quit competitive power markets by mid-2018.

Power generators including Dynegy Inc. have fought subsidies for nuclear generators, arguing that they threaten competitive power markets. Dynegy Chief Executive Officer Robert Flexon went as far as to say in April that they’re “bad for the country,” calling them a form of corporate welfare.

Meanwhile, Bloomberg New Energy Finance warned in its report Wednesday that shutting all uneconomic reactors in the U.S. would “easily vanquish” all emissions reductions the sector has made since 2012.