A key Republican defender of the wind industry expressed skepticism about what he calls an overly hasty review by the Department of Energy of electric grid security, which industry advocates say could undermine new wind investments.

In a letter sent Wednesday to Energy Secretary Rick Perry, Sen. Charles E. Grassley, R-Iowa, asked the department to provide answers about the methodology and cost of the grid review, which DOE said is intended to look at how renewable energy sources like wind make the grid less reliable.

“I understand you set a mid-June deadline for the study,” Grassley said in the letter. “I’m concerned that a hastily developed study, which appears to pre-determine that variable, renewable sources such as wind have undermined grid reliability, will not be viewed as credible, relevant or worthy of valuable taxpayer resources.”

The Energy Department is in the midst of the 60-day review of how federal energy policy is affecting the long-term reliability of the electric grid.

The review, according to a memo issued by Perry in April, is intended to examine whether the U.S. government’s energy policies adequately promote what is known as baseload power generation that runs continuously — like that provided by nuclear and coal-fired power plants — and protects against the early retirement of those power plants as a result of “market-deflating” federal policies.

The review could offer the Trump administration an opportunity to further distance itself from the Obama-era energy agenda, which emphasized clean energy sources like wind and solar at the expense of fossil fuels. Perry, President Donald Trump and most Republican lawmakers say they favor an “all-the-above” approach to energy that includes all sources, including coal.

In an earlier letter to Perry, a coalition of advocacy groups including Advanced Energy Economy, American Council on Renewable Energy, American Wind Energy Association and Solar Energy Industries Association said wind, solar and other renewable sources have made the grid “more diverse in its energy sources than ever before,” as well as “more reliable and resilient.”

For Grassley, the self-proclaimed “father” of the wind production tax credit that has spurred record investment in the technology, federal renewable policy has bolstered a technology that has helped Iowa become a national leader in electric generation from wind. The credit phases out by 2019.

“Any study reviewing the impacts of wind energy on grid reliability and security should look closely at Iowa’s utility operations as evidence of its success,” Grassley concluded.