STUDY: Keeping Diablo Canyon Power Plant Online Would Help California Decarbonize More Quickly, More Reliably and at Lower Cost

(June 9, 2022) – Extending operations at the Diablo Canyon Nuclear Power Plant, California’s largest single source of carbon-free electricity production, would significantly reduce emissions and natural gas use, and accelerate progress toward the state’s ambitious clean energy goals, according to a new study released by Carbon Free California. Retaining Diablo Canyon could help avoid blackouts, significantly reduce electric power costs and provide the best opportunity for California to meet its climate goals, even with the widespread deployment of renewables and energy storage.

The analysis, conducted by the Brattle Group, found that keeping Diablo Canyon online could also help enable California to achieve a carbon-free grid by 2035, a decade earlier than the state’s current goal, at a cost $5 billion lower than if the plant were retired. These early reductions could help jumpstart economy-wide decarbonization and reduce California’s dependence on gas-fired power generation, lowering cumulative greenhouse gas emissions by 40 million metric tons of CO2.

“Diablo Canyon is already the largest clean energy resource in California, a state that has set the ambitious goal of a carbon-free electric grid,” said Brattle Group Principal Sam Newell. “In combination with a dramatic expansion of solar, wind, storage and dispatchable clean technologies, the study shows that keeping Diablo Canyon online will help California achieve its goals faster, at less cost and with greater grid reliability.”

The study found that keeping Diablo Canyon in California’s energy portfolio could reduce costs for ratepayers by a net present value (NPV) of approximately $4 billion, even with an assumed capital investment of $2 billion to meet the state’s ocean water intake standards. These system-wide savings result from displacing gas-fired generation and fossil fuel imports and reducing other costs for resources needed to meet clean energy and reliability goals.

This report comes at a time when the Newsom Administration has indicated its interest in exploring the option of retaining Diablo Canyon and the state faces significant electricity reliability challenges. Recently released polling found that 58% of state residents believe Diablo Canyon should continue to operate, with even greater support in the local community surrounding the plant.

Brattle Group’s full analysis is available here.

What Others Are Saying

“The report, building on work from Stanford and MIT researchers, takes a hardheaded look at the benefits to California of keeping Diablo Canyon as a part of our state’s zero carbon electricity mix. Given state policymakers reconsideration of the wisdom of closing the plant, it’s worth taking a serious look at this highly credible work.”

Michael Wara
Director of the Climate and Energy Policy Program at the Woods Institute for the Environment at Stanford University

“For California to stay on track with its deep decarbonization goals everything needs to line up, especially in the electric power sector. That means massive expansion of renewable energy supplies and transmission at rates that are unprecedented. This new analysis shows that the extension of Diablo Canyon would, in effect, give California more options as it figures out how to add all these renewables. The California decarbonization plan matters mainly because it is a model for the rest of the world.  If California fails—because deep decarbonization proves infeasible or the grid becomes conspicuously unreliable—that will send a signal that could set back planetary efforts to cut emissions and slow global warming. We need to get this right, which means putting all options on the table to help the state decarbonize.”

David Victor 
Endowed chair in Innovation and Public Policy, University of California, San Diego, and director of the Deep Decarbonization Initiative

“This report by the Brattle Group provides strong and accurate support for keeping the Diablo Canyon Nuclear Power Plant up and running. California’s goals for reliable, carbon-free power will require clean firm power – power available whenever you need, for as long as you need it. In a system where inexpensive but seasonally variable solar power makes up a dominant share of the electricity portfolio, Diablo Canyon’s 2.2 Gigawatts will keep carbon out of the atmosphere while keeping the lights on in California when renewable energy isn’t available. California would be wise to keep this plant running.”

Jane Long
Associate director for Energy and Environment at Lawrence Livermore National Laboratory (ret.) and lead author of the recent study on requirements for decarbonizing California’s electric system

About Carbon Free California

Carbon Free California is funded by California-based entrepreneurs and brings together leaders from business, labor and the technology sector to focus on creating a pathway to a carbon-free future and securing the clean, reliable energy needed to power the world’s fifth-largest economy. Carbon Free California believes the state must pursue all forms of emission-free energy to address the climate crisis and achieve our urgent emission reduction goals. Extending the operation of the Diablo Canyon Nuclear Power Plant will bolster the grid with reliable carbon-free energy and enable the state to transition to increasing shares of wind and solar power, while avoiding disruptive and costly rolling blackouts. Carbon Free California receives no funding from utility or nuclear industry interests.

Learn more at or follow us on Twitter at @carbonfreeca.