Brown's office filed an appeal with the Ninth U.S. Circuit Court of Appeals in San Francisco, where the cases are likely to be consolidated.
A 1992 law requires the Energy Department to set efficiency standards for electricity distribution transformers, most of which are owned by utility companies and transmit power to homes and businesses. The department took no action until this October, when it issued standards scheduled to take effect in 2010.
In a statement in the Federal Register, the department declared that its standards "will achieve the maximum improvements in energy efficiency that are technologically feasible and economically justified." More stringent standards, the department said, would cause economic harm to the nation without significant environmental benefits.
Environmental groups challenged those statements. Ballo said utility companies had joined environmental organizations in seeking stronger standards that would reduce energy waste - saving the companies $11.1 billion - and the need for more pollution-emitting power plants.
If the department simply required new transformers to be as efficient as the best equipment already on the market, environmental organizations said, enough energy would be saved to eliminate the need for nearly 20 large power plants by 2038.
That would also reduce the annual output of heat-trapping carbon dioxide by 700 million tons, more than the amount emitted by all U.S. cars, the groups said.
The Energy Department has said one reason it did not require greater efficiency was that there was no reliable way to measure the potential economic benefits from reducing carbon dioxide emissions.
State Deputy Attorney General Janill Richards, who filed the suit for Brown's office, noted that the Bush administration made the same argument in defense of its new miles-per-gallon standards for light trucks and SUVs.
An appeals court in San Francisco rejected those standards in November and said the administration must consider the effects of fuel consumption on global warming.
The court was "very clear - the federal government can't pretend any more that controlling emissions doesn't have value," Richards said.
She said California is also among the states that have filed a similar suit challenging new federal efficiency standards for commercial air conditioning and heating units.