By Joseph Mangano
September 14, 2026
The two Diablo Canyon nuclear reactors, the last operational ones in California, now waste 30% of the wind and solar energy being produced in California—and are blocking the development of additional renewable energy. Diablo has State mandated priority for its electricity generation operations. In order to leave the nuclear power plant “on” (turning it off could subject it to a “restart” 30-day delay), Diablo “bumps” renewable energy off the grid whenever it needs to in order to operate at full capacity. Unfortunately, this automatically leads to the process of “curtailment.” Curtailment occurs when the sun is shining and the wind is blowing and the operators of those generation activities are told to “curtail” sending power to the grid, thereby “wasting” renewable energy and reducing what the operator of those benign resources are paid for their capital assets that day. This waste occurs on a rising number of days in which fast-growing renewable sources generate all the electricity needed to power the State.
Not only does Diablo Canyon – located in San Luis Obispo County – waste wind and solar energy, it is also costing taxpayers and rate payers billions of dollars to make needed mechanical upgrades to its aging and corroding parts just to remain open.
These facts, which support the growing belief that Diablo Canyon is not needed, were presented at an August 14, 2026 panel convened by numerous environmental groups and attended by staff members of 25 State legislators. Diablo Canyon – the only nuclear plant still operating in California – is licensed only until 2030. The State legislature must decide by then whether to approve a 15-year license extension or shut the aging, decrepit plant permanently.
Stanford engineering professor Mark Jacobson cited the estimated 30% waste figure in testimony to the panel. “Wind and solar actually shut down…especially during spring [when] clean renewable energy meets over 100 percent of the demand in California for up to 10 hours a day,” Jacobson said. Nuclear plants cannot abruptly shut down without safety concerns; thus, as noted above, they occupy transmission lines that would otherwise be used for wind and solar power.
Renewable sources accounted for 59% of California’s electricity in the first half of 2026, much of it wind and solar power. By contrast, Diablo Canyon’s share of consumed electricity is only 5.9%. And, on a national basis, renewables now produce more than half of the electricity in 13 U.S. states.
The cost to taxpayers and rate payers of keeping Diablo Canyon operating, in excess of the “waste” factor has exceeded $3.5 billion. These funds include:
- $1.1 billion from a no-interest loan issued by the Biden Administration
- $271 million from a loan issued by the Trump Administration
- $1.4 billion in loans from the state government
- $720 million added to electric bills by Pacific Gas & Electric, which operates the reactors
A $600 million predicted deficit for Diablo Canyon in 2027 will require additional taxpayer and ratepayer funds to close the gap.
Along with wasting renewable energy and costing taxpayers and ratepayers billions, growing evidence suggests that Diablo Canyon poses an environmental health hazard. In April, the Radiation and Public Health Project (“RPHP”) released a report on worsening health among San Luis Obispo County newborns and infants. The report noted that:
- The infant death rate moved from 16% below, to 1% above, the state rate since Diablo Canyon opened (current rates are +11% and +23% higher among white non-Hispanics and white Hispanics)
- The rate of premature births moved from 21% below, to 3% above, the state since the late 1990s.
- The rate of 12 common birth defects for babies born adjacent to Diablo was more than double the State average in 2016-2024
Diablo Canyon was also included in four journal articles published by researchers at the Harvard School of Public Health in the past eight months. These articles calculated that from 2000 to 2018, a total of 390,000 excess deaths occurred within 30 miles of U.S. nuclear plants, of which 115,000 were due to cancer.
Concerns about Diablo Canyon are growing at a time when numerous proposals to expand U.S. nuclear power have been made. The U.S. has joined 37 other nations in signing a petition to triple electricity from nuclear plants by 2050, which makes no sense form a financial, or public policy point of view. Who is “winning” if the public is losing? You guessed it: a handful of very large companies with enormous resources spent on perpetually lobbying government. The public at large will have to “wake up” and tell the government that it prefers safer, more reliable, non-deadly renewable energy in order to stop this madness.
REFERENCES
Electricity in California 2025/2026. April 2025-March 2026.
Harvard study #1 – Massachusetts – 20,000 excess cancer cases near nuclear plants, 2000-2018 https://pubmed.ncbi.nlm.nih.gov/41408632/
Harvard study #2 – U.S. – 115,000 excess cancer deaths near nuclear plants, 2000-2018 https://pubmed.ncbi.nlm.nih.gov/41730864/
Harvard study #3 – U.S. – 77,000 excess lung/breast/colon cancer death near nuclear plants, 2000-2020 https://pubmed.ncbi.nlm.nih.gov/42162233/
Harvard study #4 – U.S. – 390,000 excess deaths from all causes near nuclear plants, 2000-2018 https://link.springer.com/article/10.1007/s10654-026-01442-x