Last month, utility officials announced a plan to end its use of coal, in line with LA Mayor Antonio Villaraigosa’s plan to make the city coal-free by 2025.

LADWP wants to sell off one coal-fired power plant in Arizona and grant approvals for a second plant in Utah to be converted to run on natural gas.

The two plants together provide LA with 40% of its energy requirements.

LADWP owns a 21% interest in the 2250 megawatt Navajo generating station, receiving 477MW of coal-fired power from the plant.

It will sell its stake in Navajo to Salt River Project, ending LA’s use of coal-fired power from the plant by December 31, 2015.

LADWP also holds a long-term power sales agreement with the Utah Intermountain power plant until 2027, contractually obliging it to purchase coal until this time.

In order to meet Villaraigosa’s 2025 target, LADWP has signed a new agreement with Intermountain and its other customers to convert the plant into a combined-cycle natural gas plant by 2025.

The conversion is scheduled to begin no later than January 1, 2020.

The council approved the plan in a unanimous vote on Tuesday.

The news comes shortly after LADWP ratepayer advocate Fred Pickel said the cost of taking gas-fired energy from Intermountain power project was projected at $500 million due to high gas prices and the plan to sell the Arizona plant could cost between $150 million and $200 million.

LADWP general manager Ron Nichols assured the council that the transition process was in the early stages and many of the details were yet to come, according to the LA Times.

Nichols noted the changing costs of gas and renewable energies but said the city had until 2020 to determine the combination of natural gas and renewable energy that would be generated at the Utah plant.

In the meantime, he said, the utility would consider all alternatives.

"Our expectation is we will be coming back to you and telling you what those costs are looking like, well before we have to pull the trigger," he said.