The Diablo Canyon Nuclear Power Plant in San Luis Obispo County is the state's largest producer of electricity, and it will be difficult to replace, even with an increase in renewables.
Pacific Gas and Electric owns it and says it would consider all options.
PG&E planned to close the plant once the reactor licenses expire as part of an agreement with labor unions, environmental groups, and nuclear stakeholders.
Newsom has no direct authority over the operating license for the Diablo Canyon Nuclear Power Plant, but floated the idea that PG&E could seek a share of $6 billion in federal funding the Biden administration established to rescue nuclear plants at risk of closing.
Any proposal to extend the operating life of the plant is certain to revive an extensive battle over the plant's safety and would involve complex reviews by an array of state and federal agencies.
The issues in play at Diablo Canyon range from a long-running debate over the ability of structures to withstand earthquakes - one fault runs 650 yards (594 meters) from the reactors - to the possibility PG&E might be ordered by state regulators to spend potentially billions of dollars to modify or replace the plant's cooling system, which sucks up ocean water and has been blamed for killing fish and other marine life.
Also unclear is the plant's capacity to store additional spent fuel from the reactors. The highly radioactive waste is kept at nuclear plants, since the nation does not have a long-term disposal site.
The Associated Press contributed to this report