Environmentalists are urging the Supreme Court to uphold a landmark utility rule that if overturned would result in increased energy costs for consumers, and in the worst case, blackouts.

The case involves a spat between federal energy regulators and states on one side, and the utility industry on the other, over a regulation that compensates energy consumers for using less energy at times when the electric grid is stressed. The energy-reduction resource is commonly known in the industry as "demand response."

"By reducing the amount of power that must be transmitted at critical times, demand response helps diminish the risk of forced power plant outages and full-scale blackouts," said the Environmental Defense Fund in amicus briefs filed late last week with the high court.

The group says that "in transmission-constrained areas, where it can be literally impossible to add additional energy at peak times, demand response is uniquely able to prevent interruptions" and prevent major outages.

Environmentalists are the latest to add their voices to a flurry of briefs submitted to the Supreme Court in support of the Federal Energy Regulatory Commission's regulations.

The group also argues that the rules would help integrate increasing amounts of renewables and help President Obama meet his climate change goals.

The Supreme Court decided to take up the case in May after the commission, the nation's utility regulator, petitioned the justices to reverse the D.C. Circuit Court of Appeals decision to scrap the rule, which was established in 2012.

The court said the commission overstepped its authority in establishing the demand response market and must stop the program.

It ruled in a 2-1 decision that the commission's authority does not extend beyond the interstate wholesale electricity markets. But because the rule affected rates in the state-controlled retail markets, the federal commission exceeded its jurisdiction.

The commission and most of the Mid-Atlantic states that support the order argue that the rule helped save large swaths of the country from power outages two winters ago during the "Polar Vortex."

During the extremely cold winter, power plants were overtaxed and called upon consumers to reduce consumption at critical moments, or risk major outages.

States, environmentalists and energy consumers all raise energy reliability as a primary issue in supporting the regulations. They also argue that the rule saves consumers money, while offsetting the need for new, expensive power plant construction.

But the utility industry says the regulation distorts the energy markets overseen by the commission, which were originally intended to incentivize power plant development, not demand response.

Briefs in support of the regulation will be filed with the court through July. The power industry is slated to submit its briefs to the court by Aug. 31. Friends of the utilities, or amicus, are to submit briefs by Sept. 8.

The new Supreme Court session starts in October.