Future Diablo Canyon Closure Creates More Questions than Answers for California’s Fragile Grid

The Diablo Canyon Nuclear facility is California’s last operating nuclear power plant, but it’s living on borrowed time. The plant’s two reactors will close when their licenses expire in 2024 and 2025. What does that mean for California’s power generation? Unfortunately, there are more questions than answers, leaving energy experts concerned that the state isn’t ready for the consequences. 

“You have this huge amount of carbon-free resources that will be coming offline three to four years from now — which is in reality like tomorrow, when you’re trying to develop other new resources,” explains Jan Smutny-Jones, CEO of the Independent Energy Producers Association, “So it’s really significant that it’s going away and the question then is, what do we replace it with?” 

Diablo Canyon plays a crucial role in ensuring the reliability of power in the Golden State, providing 10% of the state’s electricity. Reliability is an essential concern in the nation’s most populous state after Californians faced rolling blackouts during a record-setting heat wave last August. As we wrote at the time, state regulators had shut down numerous baseload power plants, ignoring the California Independent System Operator’s (CAISO’s) warnings. The shutdowns cut energy supplies and all but ensured future blackouts. 

Losing another primary power source, not to mention one that’s carbon-free, will only compound the problem. Why? Because, as the CAISO warned last October, the system is headed for a “critical inflection point” after Diablo Canyon retires.

Closing Diablo Canyon will also likely impact California’s ambitious clean energy goals. That’s because the state set goals in 2018 to rely on 100% clean energy by 2045. Taking some 18,000 GWh of emission-free nuclear power offline could leave energy providers with little choice other than to turn to more emission-causing power generation methods. 

“It’s [around] 2,100 MW of power that is baseload — and so that is a particular challenge in terms of reliability, particularly since the state has had a policy of trying to move away from fossil fuels,” Dan Richard, a solo energy consultant and a former senior official at PG&E, says. 

So what can be done to address reliability issues? For many nuclear advocates, the answer is clear: end plans to close the plant. Others, however, argue that the plant will close no matter what and are calling for renewables and storage to fill the gaps instead. 

The California Public Utilities Commission (CPUC) has issued a ruling to address future reliability issues caused by Diablo Canyon’s closure, as well as the closure of several natural gas plants. The CPUC recommends procuring 7,500 MW of resources from 2023 through 2025 and has suggested using 1 GW of geothermal energy and 1 GW of long-duration storage to help meet demand. This new power supply could eventually help provide reliable, clean energy.  But will there be enough time to get them online before Diablo Canyon closes? And is long-term battery storage a viable storage option? After all, pumped hydropower facilities still account for 95% of all energy storage.

It isn’t clear how California will manage to make up for Diablo Canyon’s loss.  But what is clear is that planning has to happen now to fill the void left by the retirement of this reliable carbon-free baseload facility. Failing to do so will raise serious questions about whether Californians will have access to affordable and reliable power during the dog days of summer.