Among the subsidies the department is examining is a production tax credit that allows most wind farms to shave pennies off the price of each kilowatt-hour they send to the grid. Though flattening demand for electricity and cheap natural gas are the main forces depressing wholesale energy prices, the credit means that wind producers can often offer their power to the market at the lowest price. Sometimes, when energy demand is low and wind is strong, the credit can drive the effective price below zero.

Mr. Perry has raised the possibility of federal intervention in energy markets to protect coal and nuclear plants against lower-priced wind and natural-gas supplies. While he backed state control of market policies as Texas governor, he said at a conference in April that “the boot’s on the other foot now.”

Energy experts say that without the credit and other favorable subsidies, mandates and market policies in place, wind development and production will be threatened. When the credit has periodically expired, installations nearly ground to a halt — dropping by roughly 76 to 93 percent, according to an analysis by the Union of Concerned Scientists — only to resume again with its renewal. Congressional estimates put the cost of the credit at $3.1 billion last year, and the figure is expected to reach $4 billion this year.

“There’s no question: if the P.T.C. goes away, that’s a big number,” said Robert F. Shapiro, a lawyer at Chadbourne & Parke in Washington, who focuses on project finance and energy. “New plants would have to meet a tougher test, a market-price test, that can’t be masked in part by that subsidy.”