The possible expiration of the credit comes at a tough time for the industry. It faces an array of market challenges -- slack electric demand, competition from low-cost natural gas and some utilities questioning the need for new power plants of all kinds.
"Right now, the PTC is the immediate thing that is holding our projects up," said John Ihle, founder of PlainStates Energy, a renewable energy developer based in Breckenridge, Minn., that has approval from the state to build three wind farms in the state.
Industry officials say it is difficult to negotiate power-sales deals until Congress decides the fate of the tax credit.
RES' proposed Pleasant Valley Wind project near Austin, Minn., is the largest permitted project that hangs in limbo, facing many of the market challenges squeezing the industry.
"Utilities have seen a lessening in demand, and their desire to go out and buy new electricity is a problem," DeVito said.
Xcel Energy, for example, projects a drop in electric sales in 2013, according to regulatory filings.
Even when utilities need new power plants, increasingly they're attracted to those fueled by natural gas. With the tax credit, new wind farms can profitably sell electricity to utilities at 4 cents to 6 cents per kilowatt hour, industry officials say. While that's a competitive price for power, it's still more than the price of electricity from a new natural gas-fired generator.
"When you compare the cost of new generation, a wind farm is far cheaper than a new coal plant," said RES' DeVito. "If it wasn't for all this fracking that was making gas very competitive, wind would be the cheapest."
The American Wind Energy Association, the trade group lobbying for the credit extension, points to the Senate Finance Committee's overwhelming bipartisan approval of tax extensions including the PTC as the basis for hope.
The association has stressed the loss of 37,000 American jobs tied to wind power if the tax credit ends. AWEA also points to the outspoken support from Sens. Mark Udall, D-Colo., and Charles Grassley, R-Iowa, as well as the backing of Minnesota's two Democratic senators, Al Franken and Amy Klobuchar, and endorsements from several House Republicans.
But AWEA officials are also relying on a deficit deal to which the extension can be attached.
"It all depends on the ability of [House] Speaker [John] Boehner and the president," said Aaron Severn, AWEA's director of federal legislative affairs. "That's the train that's leaving the station, and you need to get on that train."