Pasadena, Anaheim and Riverside were also singled out by the environmental group's campaign, which criticizes the cities' long-term contracts with Utah's Intermountain Power Plant, considered one of the 20 largest coal-burning polluters in the country.
"Our message is simple," Jim Gonzalez, the group's chairman, said in a statement. "We are urging 100,000 voters to tell their local elected officials to stop using dirty coal and switch to clean renewable energy for their electricity needs."
Local utility officials countered that they are moving in that direction. Both cities have committed to buying roughly one-third of their power from renewable sources by 2020.
"We agree with the [Renewable Energy Conservation Project] kids," said Burbank Water & Power General Manager Ron Davis. "They are just out-of-date and misinformed."
In Burbank, modernized natural gas plants have already cut the utility's carbon emissions to below 1990 levels, he said.
The utility also continues to add to its renewable-energy portfolio, in turn ramping down its coal production, which Davis said is already below the 42% cited in the mailer.
Glendale gets about 23% of its power from renewable energy sources, officials said.
"We are working very diligently to offset our carbon emissions while maintaining our interest in the coal plants," said Glendale Water & Power General Manager Glenn Steiger. "I would argue that a dirty cloud does not hang over Glendale."
Steiger added that the power the city receives from coal plants in Utah and New Mexico is reliable and inexpensive, which helps keep rates low.
"Actually, they've turned out to be extraordinarily good options for us," he said.