California's last nuclear plant, Pacific Gas and Electric’s (PG&E’s) Diablo Canyon plant in San Luis Obispo County, will close in 2025, the California Public Utilities Commission (CPUC) said on 11 January. The CPUC's five commissioners unanimously approved a revised version of the joint proposal for Diablo Canyon's closure that was put forward by PG&E together with labour and environmental organisations.

California law bans the construction of any more reactors until the federal government establishes a long-term policy on dealing with nuclear waste. The two 1100MWe pressurised water reactors (PWRs) at Diablo Canyon began operation in 1985 and 1986, and produce 9% of the state's electricity. They will close in 2025 and 2026 when their operating licences expire.

All other nuclear plants in California have already closed. Units 2 and 3 at Southern California Edison's San Onofre nuclear generating station were prematurely retired in 2013. SONGS 1 operated from 1968 to 1992, and the single-unit Rancho Seco PWR was retired in 1989 following a referendum held in the wake of the Chernobyl accident.

PG&E said it would replace the power lost by the closure by increasing energy efficiency and use of renewable energy and employing energy storage methods exceeding current state mandates. However, CPUC did not approve PG&E's proposals for the procurement of resources to replace Diablo Canyon's output and said this should be addressed in CPUC's separate planning proceeding on electric procurement policies and programmes. It also denied a request for $85m from ratepayer funding for a community impact mitigation programme. The regulator said PG&E "may choose to use shareholder funds" to support the programme, which would aim to mitigate some of the adverse economic impacts to residents.

PG&E said it appreciated CPUC's “thoughtful consideration of this complex issue and its approval of certain elements” but expressed disappointment that the full employee retention programme and the community impact mitigation and energy efficiency programmes were not approved.

Those proposing closure included the International Brotherhood of Electrical Workers Local 1245, Coalition of California Utility Employees, Friends of the Earth, Natural Resources Defense Council, Environment California, California Energy Efficiency Industry Council and Alliance for Nuclear Responsibility. However, they supported PG&E in obtaining state approvals to enable Diablo Canyon to operate until the end of its current licences.