Diablo Canyon Power Plant

The Diablo Canyon Power Plant is a nuclear power plant near Avila Beach in San Luis Obispo County, California. Following the permanent shutdown of the San Onofre Nuclear Generating Station in 2013, Diablo Canyon is now the only operational nuclear plant in California, as well as the state's largest single power station. It was the subject of controversy and protests during its construction, with nearly two thousand civil disobedience arrests in a two-week period in 1981.

The plant has two Westinghouse-designed 4-loop pressurized water reactors operated by Pacific Gas & Electric (PG&E). Together, the twin 1100 MWe reactors produce about 18,000 GW·h of electricity annually (8.6% of total California generation and 23% of carbon-free generation), supplying the electrical needs of more than 3 million people. For 2026 forward, facility operations and maintenance costs are projected to be $0.03 per kWh generated, but when including new fees authorized by a recent law, that number rises to $0.08 per kWh. Intermittent sources like wind and solar cost $0.05 and $0.06 per kWh without battery storage, but $0.09 and $0.14 with battery storage.

Though it was built less than a mile from the Shoreline Fault line, which was not known to exist at the time of construction, and is located less than three miles (4.8 km) from the Hosgri fault, a 2016 Nuclear Regulatory Commission (NRC) probabilistic risk assessment of the plant, taking into account seismic risk, estimated the frequency of core damage at one instance per 7.6 million reactor years. The plant is located in NRC region IV.

In 2016, PG&E announced that it plans to close the two Diablo Canyon reactors in 2024 and 2025, stating that because California's energy regulations give renewables priority over nuclear, the plant would likely only run half-time, making it uneconomical. (Nuclear plants are used for base load in order to spread their large fixed costs over as many kWh of generation as possible.) In 2020, experts at the California Independent System Operator (CAISO) warned that when the plant closes the state will reach a "critical inflection point", which will create a significant challenge to ensure reliability of the grid without resorting to more fossil fuel usage, and could jeopardize California's greenhouse gas reduction targets. In 2021 the California Energy Commission and CAISO warned that the state may have summer blackouts in future years as a result of Diablo's closure coinciding with the shutdown of four natural gas plants of 3.7GW total capacity, and the inability to rely on imported electricity during West-wide heat waves due to reduced hydroelectric capacity (from the decades-long drought) and the closure of coal plants. A 2021 report from researchers at MIT and Stanford states that keeping Diablo Canyon running until 2035 would reduce the state's carbon emissions from electricity generation by 11% every year, save the state a cumulative $2.6 billion (rising to $21 billion if kept open until 2045), and improve the reliability of the grid. Full decommissioning of the plant is estimated to take decades and cost nearly $4 billion.

2021-22 Senate Bill 846 (Dodd) extended the plant's operations through 2030.