While California remains the nation's leader in carbon-free power, nuclear will no longer be in its arsenal.

On Jan. 11, the state's energy regulator, the California Public Utilities Commission (CPUC), approved a proposal from Pacific Gas and Electric (PG&E) to retire its nuclear plant at Diablo Canyon.

The utility proposed not renewing the licenses for the plant's two reactors, Unit 1 and Unit 2, when they expire in 2024 and 2025, respectively. The CPUC approved the proposal on a unanimous vote of 5–0.

PG&E had announced its intentions to retire Diablo Canyon in the summer of 2016. Located in San Luis Obispo County roughly halfway between San Francisco and Los Angeles, it is California's largest power plant, producing 9 percent of the state's electricity. It is also one of the county's largest employers with a payroll of 1,500.

Like all nuclear plants, Diablo Canyon has faced controversy since it was built more than 30 years ago. Situated along a coastal bluff, environmentalists have long feared a nuclear disaster. The location is in proximity to several earthquake fault lines, one of which was discovered only a few miles away from the site during the construction phase.

Calls for closure escalated in 2011 after an earthquake triggered a nuclear disaster at the Fukushima nuclear plant in Japan. The changing economics of energy in California further precipitated plans to close the facility. PG&E previously had stated that with the state placing greater emphasis and investment on renewables and energy efficiency, the nuclear plant would eventually be too expensive to operate.

As part of the proceedings, the CPUC approved PG&E's plan to recover $241.2 million for retirement costs, most of which will go toward employ retention. Skilled workers will be retained for the next seven years as the reactors are prepared for retirement.