A one-year extension of the credit, which is set to expire at the end of this year, was tacked on as an amendment to a transportation bill now before the chamber.
Lawmakers voted 49-49 for the proposal, offered by Michigan Democrat senator Debbie Stabenow, but 60 votes were needed for approval.
The vote came as a disappointment to the wind industry, which has repeatedly warned that unless an extension is passed soon, thousands of jobs in the sector will be lost.
"The clock is ticking, and the stakes for a timely extension of the PTC could not be clearer," said AWEA CEO Denise Bode. "With every day that goes by, layoffs are occurring and further job losses - and even plant closings - will accelerate with each month we near expiration in December."
The industry, Bode said, will continue to look for opportunities to win an extension. But many expect the next main window of opportunity to get the extension approved by lawmakers won’t come until after the November presidential election.
The new could have been worse for the wind industry, however. South Carolina Republican senator Jim DeMint proposed his own amendment calling for the repeal of all energy tax credits, including the PTC. It was defeated by a 72-26 margin.