The Diablo Canyon NPP in the US state of California is set to be permanently shut down by 2025, under a proposal announced on 21 June by plant operator Pacific Gas & Electric (PG&E). The proposal was put forward jointly with unions and environmental organisations to reflect "California’s changing energy landscape". PG&E said the move "would increase investment in energy efficiency, renewables and storage beyond current state mandates while phasing out PG&E’s production of nuclear power in California by 2025".

PG&E proposes to retire the twin unit Diablo Canyon at the expiration of its current Nuclear Regulatory Commission (NRC) operating licences, assuming the relevant regulatory procedures are met. "The parties will jointly propose and support the orderly replacement of Diablo Canyon with greenhouse gas free resources," PG&E said.

"Recognising that the procurement, construction and implementation of a greenhouse gas free portfolio of energy efficiency, renewables and storage will take years, the parties recognise that PG&E intends to operate Diablo Canyon to the end of its current NRC operating licences, which expire on 2 November 2024 (unit 1 – 1,122MWe) and 26 August 2025 (unit 2 – 1,118MWe)," PG&E said. Both units are Westinghouse pressurised water reactors. The detailed phase out proposal will now go to the California Public Utility Commission for consideration.

The US Nuclear Energy Institute (NEI) said Diablo Canyon’s closing "will remove nearly 24% of the state’s clean electricity from the grid by 2025". The plant’s two reactor units prevent the emission of up to 7m tonnes of carbon dioxide each year, the NEI said.
NEI president and CEO Marvin Fertel said: "This agreement is unique to PG&E and California energy policy. In other states, energy companies have extended the operation of 80 reactors as a strategic measure to retain reliable, carbon-free electricity. We recognise that this decision is a difficult one for hundreds of employees who have operated Diablo Canyon safely and professionally for three decades." However, he said it was "imperative that state and federal policymakers provide mechanisms now that recognise the full value of NPPs in a diverse electricity supply portfolio".

In the agreement, PG&E commits to renewable energy providing 55% of its total retail power sales by 2031, voluntarily exceeding the California standard of 50% renewables by 2030. A technical and economic report commissioned by Friends of the Earth served as a critical underpinning for the negotiations. The report, known as "Plan B," provided a detailed analysis of how power from the Diablo Canyon reactors could be replaced with renewable, efficiency and energy storage resources which would be both less expensive and greenhouse gas free.

The agreement also contains provisions for the Diablo Canyon workforce and the community of San Luis Obispo. "We are pleased that the parties considered the impact of this agreement on the plant employees and the nearby community," said Pica. "The agreement provides funding necessary to ease the transition to a clean energy economy."

However, even after Diablo Canyon closes, Southern California will still get a small percentage of its electricity from Arizona’s 4,000MWe Palo Verde NPP. Palo Verde is owned by Southern California Edison, the Los Angeles Department of Water and Power, and the Southern California Public Power Authority, whose members include municipal power companies supplying Glendale, Pasadena, Burbank and Anaheim.