It might seem like everyone from venture capitalists to the news media to the U.S. secretary of Energy has been hyping small modular reactors as the key to unlocking a nuclear renaissance and solving both climate change and modern data centers’ ravenous need for power.
On Monday, the Natural Resources Committee of the California Assembly will consider a bill to repeal a longstanding moratorium on nuclear plants in the state, which was meant to be in place until there is a sustainable plan for what to do with radioactive waste. Defeated multiple times in the past, this bill would carve out an exception for small modular reactors, or SMRs, the current pipe dream of nuclear advocates.
SMRs are typically under 300 megawatts, compared with the combined 2.2 gigawatts from Diablo Canyon’s two operating reactors near San Luis Obispo. These smaller nukes have received so much attention in recent years mainly because modern reactors are so costly that the U.S. and Europe have all but stopped building any.
The sad truth is that small reactors make even less sense than big ones. And Trump’s tariffs only make the math more discouraging.
I’ve been analyzing nuclear power since 1993, when I started a five-year stint at the Department of Energy as a special assistant to the deputy secretary. I helped him oversee both the nuclear energy program and the energy efficiency and renewable energy program, which I ran in 1997.
So I know all too well that the hype is built on quicksand — specifically, a seven-decade history of failure. As a 2015 analysis put it, “Economics killed small nuclear power plants in the past — and probably will keep doing so.” A 2014 journal article concluded many of those “building support for small modular reactors” are putting forward “rhetorical visions imbued with elements of fantasy.”
But isn’t there a nuclear renaissance going on? Nope. Georgia’s Vogtle plant is the only new nuclear plant the U.S. has successfully built and started in recent decades. The total cost was $35 billion, or about $16 million per megawatt of generating capacity — far more than methane (natural gas) or solar and wind with battery storage.
As such, Vogtle is “the most expensive power plant ever built on Earth,” with an “astoundingly high” estimated electricity cost, noted Power magazine. Georgia ratepayers each paid $1,000 to support this plant before they even got any power, and now their bills are rising more than $200 annually.
The high cost of construction and the resulting high energy bills explain why nuclear’s share of global power peaked at 17% in the mid-1990s but was down to 9.1% in 2024.
For decades, economies of scale drove reactors to grow beyond 1,000 megawatts. The idea that abandoning this logic would lead to a lower cost per megawatt is magical thinking, defying technical plausibility, historical reality and common sense.
Even a September report from the federal Department of Energy — which funds SMR development — modeled a cost per megawatt more than 50% higher than for large reactors. That’s why there are only three operating SMRs: one in China, with a 300% cost overrun, and two in Russia, with a 400% overrun. In March, a Financial Times analysis labeled such small reactors “the most expensive energy source.”
Indeed, the first SMR the U.S. tried to build — by NuScale — was canceled in 2023 after its cost soared past $20 million per megawatt, higher than Vogtle. In 2024, Bill Gates told CBS the full cost of his 375-megawatt Natrium reactor would be “close to $10 billion,” making its cost nearly $30 million per megawatt — almost twice Vogtle’s.
All of this has played out against a backdrop of historically cheap natural gas and a rapid expansion of renewable energy sources for electricity generation. All that competition against nuclear power matters: A 2023 Columbia University report concluded that “if the costs of new nuclear end up being much higher” than $6.2 million per megawatt, “new nuclear appears unlikely to play much of a role, if any, in the U.S. power sector.” R.I.P.
SMRs are just one of several wildly overhyped false promises on which the world is poised to spend hundreds of billions of dollars by 2040, including hydrogen energy and direct air carbon capture.
But nuclear power is the original overhyped energy technology. When he was chairman of the Atomic Energy Commission, Lewis Strauss — the Robert Downey Jr. character in “Oppenheimer” — predicted in 1954 that our children would enjoy nuclear power “too cheap to meter.”
Yet by the time I joined the Department of Energy in 1993, nuclear power costs had grown steadily for decades. Since then, prices for new reactors have kept rising, and they are now the most expensive power source. But solar, wind and battery prices have kept dropping, becoming the cheapest. Indeed, those three technologies constitute a remarkable 93% of planned U.S. utility-scale electric-generating capacity additions in 2025. The rest is natural gas.
China is the only country building many new nuclear plants over the next five years — about 35 gigawatts. Less than 1% of this projected capacity would be from small reactors — while more than 95% will be from reactors over 1,100 megawatts. Now compare all that to the 350 gigawatts of solar and wind China built — just in 2024.
For the U.S., President Trump’s erratic tariffs make small modular reactors an even riskier bet. If the U.S. economy shrinks, so does demand for new electric power plants. And the twin threats of inflation and higher interest rates increase the risk of even worse construction cost overruns.
Also, China, Canada and other trading partners provide critical supply chain elements needed to mass-produce SMRs — and mass production is key to the sales pitch claiming this technology could become affordable. That logic would apply only if virtually all of the current SMR ventures fail and only one or two end up pursuing mass production.
So, can we please stop talking about small modular reactors as a solution to our power needs and get back to building the real solutions — wind, solar and batteries? They’re cheaper and cleaner — and actually modular.
Joseph Romm is a former acting assistant secretary of Energy and the author of “The Hype About Hydrogen: False Promises and Real Solutions in the Race to Save the Climate.”
