When an obscure nonprofit group attacked one of California’s signature green-energy projects this summer — warning a congressional panel that the embrace of solar energy would lead to crippling hikes in electricity bills — officials in the state shrugged off the testimony as noise from the fringe.

With Donald Trump’s election, however, that group, the Institute for Energy Research, has moved suddenly from the fringe to the center of power. The president-elect has sent the group’s president, a former Koch Industries lobbyist named Thomas Pyle, to the Energy Department to take charge of its transition.

For years, Pyle has led a coordinated national assault on renewable power. His groups and others that belong to the sprawling network bankrolled by Charles and David Koch, whose vast fortune stems originally from oil refining, pressure lawmakers to roll back policies that promote green power. The Koch network gave Pyle’s groups $3 million in 2015.

Now, in his role with the Trump transition, Pyle’s vision will shape the new direction of a federal agency that has been a crucial partner to California and like-minded states in their embrace of solar, wind and geothermal power.

Days before he was appointed to the role, Pyle, who did not respond to interview requests, tweeted that he expected the new administration would go beyond a mere rollback of President Obama’s climate-change actions and bring about “a reset of a generation of failed energy and environmental policies.”

The impending shift would return California and other states to where they were more than a decade ago when they first began putting aggressive climate-change policies in place — swimming against the tide of a federal government antagonistic to their mission.

After years of growth, state programs to foster renewable energy are considerably more durable now and are positioned to withstand federal abandonment. But a Department of Energy guided by Koch principles could still create complications.

The industrial-scale desert solar operations that power tens of thousands of California homes, for example, were built with considerable financial backing from the Energy Department. The agency’s national laboratories in the West have been incubators for next-generation renewable-energy technologies. The department has taken a lead in encouraging other states to pursue California-style programs.

“It is inevitable with the Koch brothers already showing they have so much influence in this administration, that it will do everything in its power to inhibit the growth of renewables,” said Bryan Miller, a lobbyist for green-energy firms.

Pyle’s influence reflects how wide the Koch network’s reach has grown in Republican politics.

His ascent is particularly notable since it follows an election in which David and Charles Koch refused to put their formidable political machine to work helping get Trump elected.

Pyle’s groups, the Institute for Energy Research and the American Energy Alliance, reject the findings of most mainstream scientists regarding climate change.

They specifically dismiss as overblown the warnings from scores of published academics that a global temperature rise of more than 2 degrees Celsius, or 3.6 Fahrenheit, would be devastating. Preventing a rise in temperatures of that scale is at the root of the global climate agreement the United States and 195 other countries signed last year in Paris.

Pyle’s groups are pushing for Trump to make good on his vow to scrap that deal.

“The economic damages incurred achieving that goal would be greater than the damage caused by a warming world,” said Daniel Simmons, vice president for policy at the Institute for Energy Research.

The institute and the alliance also receive money from oil, gas and coal companies, but won’t say which ones. Bankruptcy court records show contributions from Peabody Energy and Alpha Natural Resources, two coal-mining firms. Exxon says it gave the groups money years ago, but stopped.

The institute is a favored think tank among climate skeptics, regularly reaching past mainstream climate scientists to produce contrarian research reports that it and other Koch-funded activists use in lobbying lawmakers.

“They fund research and citable material that fits with the Koch network ideology, and which can be used for its political goals,” said Robert Maguire of the Center for Responsive Politics, a nonpartisan group that tracks the impact of money on politics and policy.

“They can then go to lawmakers and say, ‘these energy experts say this is what you should do.’”

In lobbying against state laws that require utilities to generate a share of their electricity from green sources, the institute regularly cites a study from Spain that concluded more than two jobs are lost for every new green-energy job created.

The study became such a prominent talking point in state legislatures and Washington that the Spanish government sent a letter to Congress in 2009 highlighting what it said were flaws in the study’s methodology and data and noting that several other studies had concluded the opposite.

Yet the study continues on as a central talking point for the institute, a decision Simmons defends by pointing to Spain’s phasing out of some solar and wind subsidies.

“I think history shows our reports were accurate,” he said.

In 2014, the group’s research helped score the first big win for the Koch network’s crusade against such mandatory renewable-energy quotas when lawmakers in Ohio voted to temporarily roll back their state’s law.

Back in Congress, the Koch network had been leading efforts to end a multibillion-dollar Department of Energy loan-guarantee program that helped jump-start many of the country’s major green-energy projects.

The “No More Solyndras Act” — named for the California solar company that went bankrupt after receiving its loan guarantees — passed the House in 2012 but died in the Senate.

The American Energy Alliance wrote lawmakers warning them that voting against the bill would “indicate your disregard for fiscal discipline and your unwillingness to rein in wasteful spending of taxpayer money.”

Despite such dire forecasts, the Government Accountability Office reported this year that the program was running under budget. The White House said the loss rate on the department’s loan portfolio was only 2%, even after accounting for the losses incurred by Solyndra and some other failed renewable-energy companies.

Despite those successes, the Institute for Energy Research continues to attack the program. In testimony before a congressional committee in July, Simmons took aim at the Ivanpah power plant, an industrial-scale solar facility in the Mojave desert that uses next-generation technology to provide electricity to Californians.

A partnership of companies, including Google, tapped federal subsidies to build the plant.

“It is unseemly that the American taxpayer has contributed billions of dollars to these facilities,” Simmons said in his testimony. “The owners could have financed these projects.”

In the next year, the Energy Department will have some $40 billion at its disposal to distribute as new loans. That money can go to clean-energy innovations, but it can also go to coal, gas or nuclear efforts. Pyle has made clear his preference — as has Trump.

Come January, pioneering green-energy projects can start expecting a much colder winter.