A new study is challenging Energy Secretary Rick Perry's concerns about increasing levels of renewable energy in the U.S. electric grid, arguing that the decline of coal in the nation's power mix is driven largely by market forces and is not hurting the reliability of the grid.

Perry in April ordered a 60-day grid review looking in particular at whether government support for renewable energy is speeding the retirement of coal and nuclear plants and resulting in a more fragile electricity supply. He suggested in his memo that renewable energy and regulatory burdens on coal were to blame for an "erosion of critical baseload resources."

The new study says that that fear is baseless, and it argues the opposite.

It cites, among other evidence, the latest annual analysis of grid reliability conducted by the North American Electric Reliability Corporation (NERC), which found that most metrics of grid reliability are either improving or staying the same. For example, 2015 saw a drop in the number of incidents causing a temporary loss of supply. Frequency and voltage has remained stable as the amount of power from renewable energy sources has grown, it said, and the industry has been getting better at modeling changes to the grid to assess risks.

"The retirement of aging or uneconomic resources has not led, in any region, to an observed reduction in BPS (bulk power system) reliability from either resource adequacy or system security perspectives," the study says.

The report was released Tuesday by the American Wind Energy Association and the Advanced Energy Economy, which represents a broad range of corporations, including some renewable energy companies and utilities. The groups had earlier written to Perry, criticizing the department for not opening the rushed grid review to public comment—including from the renewable energy industry.

"Recently, some have raised concerns that current electric market conditions may be undermining the financial viability of certain conventional power plant technologies ... and thus jeopardizing electric system reliability. In addition, some have suggested that federal and state policies supporting renewable energy are the primary cause of the decline in financial viability. The evidence does not support either hypothesis," says the report, which was written by energy consultants, including a former Department of Energy official and state utility commissioner.

Perry selected Travis Fisher, a political appointee who previously worked for the Institute for Energy Research, an organization that favors fossil fuels, to lead his review. In a budget hearing earlier this week, Perry said the review would be completed by the end of the month. But on Wednesday, DOE spokeswoman Shaylyn Hynes told E&E News that that date had been moved back to July.

In recent years, power companies have retired more capacity from coal than from any other fuel source, while adding primarily natural gas and some renewables.

Citing data from wholesale energy markets, the report says that shift has been driven primarily by the low price of gas and advancements in the efficiency of new gas generating units. While it says government policies supporting energy efficiency and renewables have played a role, too, their influence is "a distant second to market fundamentals."

A spokesman for Edison Electric Institute, which represents utilities, said they not had yet reviewed the study and couldn't comment.

In his memo calling for the review, Perry wrote that grid experts had expressed concerns about "the diminishing diversity of our nation's electric generation mix and what that could mean for baseload power and grid resilience." He also voiced strong support for baseload power plants "that run 24-7" during budget hearings this week on Capitol Hill, where Perry made clear to members of Congress that the Trump administration's vision is to keep coal plants running and to build oil pipelines.

In a not-so-veiled swipe at the coal industry, the new report says that over the past few decades, as market and policy changes such as deregulation have reshuffled the nation's energy mix, established entities have charged that the changes would hurt reliability. Those concerns never came to pass, the report says, because of the nation's robust system of safeguards.

The review will surely face strong opposition if it tries to push the scales in favor of coal. On Wednesday, Perry's predecessor as energy secretary, Ernest Moniz, announced the formation a new organization, staffed with former Energy Department officials and MIT experts, to promote innovation in low-carbon energy technology and energy policies for a cleaner energy future.