PG&E’s plan to close the Diablo Canyon nuclear power plant -- a facility that currently provides about 10 percent of California’s electricity -- marks a historic transition for the electric power industry.  Not only does it signal the end of nuclear power in California, but it also ushers in a new way of thinking about the very foundations of our electric system.

Much has (rightly) been made of PG&E’s commitment to close the nuclear facility without increasing greenhouse gas emissions. This low-carbon future is now possible because the costs of solar and wind power have declined dramatically over the past five years, while the performance and reliability of these technologies have been proven, and they are attracting more and more investment.  

Less commented on is that closing Diablo Canyon, coming on top of the shutdown of the San Onofre nuclear power plant three year ago, means that California’s electric grid will be largely free of baseload power plants. Going forward, California’s electric power system will be operated in a very different manner than it has been for the last 100 years.

Since the days of Thomas Edison and George Westinghouse, the foundation of the electric grid has been power plants that run flat-out 24 hours a day for most of the year. Throughout the 20th century, these baseload power plants became ever bigger, with nuclear power plants like Diablo Canyon capable of producing thousands of megawatts. 

Starting in the 1980s, solar and wind power plants, driven forward by national energy policies like the Public Utilities Regulatory Policy Act (PURPA) and state-enacted renewable portfolio standards, began to be connected to the electric grid. Early on, many utilities warned that these variable output technologies would make the grid unstable and couldn’t be counted on to provide reliable power around the clock. 

The PG&E agreement to close Diablo Canyon shows that those fears have been outpaced by innovation. It is now possible to envision an energy future where the grid will be balanced moment to moment by a combination of energy storage, responsive load and fast-ramping technologies like fuel cells. In fact, an entire section of the agreement PG&E reached with environmental groups like Friends of the Earth, Environment California and the Natural Resources Defense Council addresses the issue of grid stability and reliability through resource integration and energy storage. 

This key section of the agreement acknowledges that the removal of a large baseload unit during periods of peak solar production will reduce the need for the periodic curtailment of renewable resources. It also calls on regulators to give serious consideration to PG&E’s development of large-scale energy storage projects, including pumped hydro storage like the Helms Pumped Storage Plant located 50 miles east of Fresno.

The Helms project, which began operating in 1984, was supported by regulators because it was assumed there would be excess power at night from California’s baseload nuclear power plants. Now the opposite is occurring.  As more and more solar power gets connected to the grid both in front of and behind the meter, there is the potential for excess power being generated in the middle of the day.  The 1,212-megawatt Helms project and other sources of energy storage can be used to absorb excess solar power and dispatch it later in a flexible manner when consumers need the power. 

The success of California’s transition to a more flexible and resilient power system should be seen as a model for the rest of the country. It has become increasingly obvious over the last few years that nuclear power is an economic albatross. Utilities in the Midwest, Mid-Atlantic and Northeast can no longer economically operate many plants. Meanwhile, many coal plants have reached the end of their useful lives, and others will need to be retired early to reduce greenhouse gas emissions.  

With the plan to close Diablo Canyon and PG&E’s commitment to reach 55 percent carbon-free power by 2031, it should be increasingly clear to those responsible for electric resource planning at the state, regional and national levels that the era of baseload power is coming to an end. Utility regulators and energy policymakers across the country should take notice of what’s happening in California and set in place processes that take full advantage of the modern, low-cost clean energy options available throughout the United States.   


Ed Smeloff has over 30 years of experience in energy policy and solar business development. Before joining Vote Solar, he worked for more than eight years at SunPower as director of utility and power plant sales. He was responsible for developing more than a gigawatt of that company's solar power plants in the United States and initiated solar business development in Mexico.