Solar and Nuclear Both Must Live. Energy Technology Fanaticism Needs to Die.

Why Solar Optimism and Solarmaxxing Are Not the Same Thing

Every year or so, for as long as either of us can remember, there is a great Twitter/X pile-on from a segment of the clean tech and climate movement attacking the Breakthrough Institute for having been insufficiently bullish about solar energy and renewables. Our long-standing take on solar and renewables—that they are an important and growing part of the global energy mix, deserving of appropriate policy support, but nowhere close to a complete replacement of fossil fuels—is far from the most controversial stance we have taken over the years. But the intensity of these attacks often takes friends of ours in the broader abundance, progress, and techno-optimist communities by surprise because they often come from figures who are not the usual green, degrowth, or left-wing suspects.

When Noah Smith tweets that “The Breakthrough Institute will be a recurring minor comic villain in the eventual history of the energy revolution” or futurist Ramez Naam accuses us of generating “terrible solar projections” and deliberately attempting “to cast doubt on renewables,” it is jarring because on most subjects, there just isn’t some radical divergence in worldview between us. We’re all champions of abundance and progress. We are all pro-growth and pro-technology and have little use for degrowth. Neither Smith nor Naam is a technological decel like most of our anti-nuclear, anti-biotech critics. So what gives?

On the one hand, Smith’s and Naam’s problem with Breakthrough stems from a simple unwillingness to acknowledge our actual views on solar, nuclear, and energy transitions. We have, for the record, never argued that “nuclear – and only nuclear – must be the energy source of the future,” a position that Smith erroneously ascribed to us. Nor have we ever produced our own solar projections, as Naam repeatedly claimed.

A decade or more ago, we cited mainstream forecasts, from the International Energy Agency, the US Energy Information Agency, BP, and other analysts, which projected that global adoption of wind and solar energy would be much lower than ended up being the case. Notably, most of these projections were made as the enormous scale of Chinese clean tech industrial policy, mercantilism, and/or overproduction depending upon one’s perspective, was only beginning to become apparent. Typically, we noted that we thought real-world deployment would be higher than these projections. And in general, we cited those projections both to make the case for continued policy support for wind and solar, including subsidies and deployment mandates, and to push back against the idea that these sources of variable renewable energy could do most, if not all, of the heavy lifting when it came to decarbonizing the global economy.

On the other hand, the misrepresentation of our position and history on these questions by Smith, Naam, and others is not merely one of misunderstanding. Rather, it is another illustrative manifestation of the solarmaxxers’ hubris. Smith’s truculence in particular is testament to the widespread teleological faith that falling photovoltaic costs will beget permanent dominance of energy systems by solar, which has led many advocates to dismiss or even obstruct progress in other energy technologies. This has always been the basis of Breakthrough’s critiques of renewable energy maximalism. The most prominent champions of solar power—figures like Amory Lovins, Mark Jacobson, Bill McKibben, and many more—have leveraged the vision of a solar utopia to advance openly anti-nuclear policies, as well as other policies that make energy affordability, abundance, and decarbonization harder, not easier.

Making the case for nuclear energy in particular, and for all-of-the-above energy innovation in general, has required pushing back on the Lovinsian solar maximalism in which Smith and Naam are trafficking, whether wittingly or unwittingly. And in one sense, we’re happy to take one side in this dispute. Time and tide will tell whether the future is mostly solar-powered or mostly nuclear-powered or, indeed, a healthy mix of the two technologies.

What’s more pernicious about the solarmaxxers is not that they represent the other side of an open, even-odds game of technological advocacy, but that they charge their opponents as the more tribalist of the two camps, when the truth is more often precisely the opposite. Despite having consistently promoted a growing and substantial role for wind and solar energy in the global economy and supported policies to accelerate that growth for over two decades, we are branded as being against wind and solar by these critics because in their eyes, anything much short of promoting 100% renewables as being desirable, feasible, and inevitable is deemed to be “anti-renewables.”

Breakthrough has long been a special source of anger to this crowd because we played such a major role in creating the investment-centered paradigm that has accounted for much of the progress that wind, solar, batteries, and electric vehicles have made over the last 15 years, and yet refuse to sign on to the maximalist gospel that most proponents preach. In the land of solar maximalism, supporting a diverse portfolio of energy technologies and being open to a diverse range of possible energy futures makes one an enemy.

Twenty Years of Solar Optimism

To understand our dispute with the solarmaxxers, you have to go back to the beginning. Long before either Smith or Naam was prognosticating on energy, the Breakthrough Institute was a fairly lonely voice making a quixotic case for massive state investments in expensive but promising renewable energy technology.

Across most of the aughts, the overwhelming focus of the environmental community on climate change was to regulate emissions. Insofar as there was any debate within the community, it was between proponents of traditional command and control regulatory policies and market-based trading schemes. Environmental philanthropy went all-in on the $100 million “Design to Win” effort to pass a cap-and-trade program. During this period, Breakthrough was arguably the most prominent public critic of this strategy, arguing that pricing carbon wouldn’t ultimately achieve much decarbonization so long as solar, wind, batteries, nuclear, and other low-carbon technologies remained significantly more expensive than incumbent fossil fuels.

This has largely become conventional wisdom even among mainstream greens today. But it was controversial at the time. Joe Romm wrote in response that “pollution limits are far, far more important than R&D for what really matters.” David Roberts argued that “a price on carbon would do more to stimulate productive energy research than targeted grants for specific research programs.” And Brad Plumer, then a young blogger at the New Republic, described Breakthrough’s preference for “subsidizing clean-energy sources” as “weird.”

Weird or not, our investment-centered clean tech optimism was based on an understanding of the history of energy innovation that would become central talking points for a growing chorus of solar champions. In a 2008 essay for the Harvard Law and Policy Review titled “Fast, Clean, & Cheap.” we proposed a massive public buydown of the cost of solar energy, arguing that “solar has special potential, and merits special attention. Solar panels, like microchips, have their own kind of ‘Moore’s Law’: the price of solar comes down roughly 20% every time production capacity is doubled.” Not long after, we released an influential report called “Where Good Technologies Come From,” arguing that public investment in R&D, demonstration, and deployment had played a critical role in the commercialization of most transformative technologies throughout American history and that similar policies would be necessary to achieve a clean energy transition. Naam, by contrast, wouldn’t write his first post about a Moore’s Law for solar until 2011. Smith wouldn’t publish anything about solar until 2012.

With our partners at Third Way, ITIF, and elsewhere, we made the public case for investments to drive down the price of solar, wind, and other clean technologies. Breakthrough’s renewables advocacy helped lead to tens of billions of investments in the 2009 Recovery Act. Our research was cited in congressional hearings and called out multiple times in President Obama’s State of the Union addresses.

But over time, as we gained a better understanding of energy systems and technologies, a couple of things became clear to us. The first was that electrifying most end uses of energy, dramatically increasing the global demand for energy, and then running that system overwhelmingly on intermittent renewables was a fantasy, and that what would become known as “clean firm” technologies, especially nuclear, would be essential to energy abundance and decarbonization. The second was that the fiercest champions of renewables were almost always fierce opponents of nuclear power.

This was circa 2010, in the years immediately before and after Fukushima and in the midst of America’s faltering “nuclear renaissance.” It was also in the midst of flatlining demand for electricity in the wake of the Great Recession, with cheap shale gas and subsidized renewables further depressing the wholesale electricity costs that baseload nuclear plants depended on for their operations. Environmental groups and so-called ratepayer advocates were in open war against nuclear plants like Diablo Canyon and Indian Point. There were no notable next-generation nuclear startups compared to the dozens that exist today. There was no civil society pro-nuclear movement, because the Breakthrough Institute hadn’t yet launched it.

The climate movement, led by figures like Bill McKibben and Robert Kennedy Jr., insisted that declining renewable energy costs heralded not just the end of fossil fuels but of nuclear power too. These claims were not new. They had been around since long before anyone had ever heard of climate change, dating to the mid-1970’s, when Rocky Mountain Institute founder Amory Lovins invented the original solarmaxxing imaginary, the “soft energy path,” not as a solution to climate change or even a replacement for fossil fuels (Lovins, in the 70’s, actually advocated for decentralized mini-coal generators for residential use) but as an alternative to nuclear energy.

Lovins famously claimed in the early 1980s that solar was already cheaper than both fossil fuels and nuclear and forecast that solar would account for a third of US energy generation by the year 2000, a forecast that solarmaxxers conspicuously ignore when pointing the finger at erroneous solar predictions. By the early 1990s, the soft energy path had become the basis for virtually all environmental advocacy in the United States and globally.

The renewable energy avatar for a new generation of green activists is a former atmospheric scientist named Mark Jacobson, who since 2009 has produced modeling that purports to show that the world’s energy consumption could easily and quickly be met by 100% wind, water, and solar. Jacobson’s modeling was always transparent first-order nonsense. Even many energy modelers who have long been extremely bullish on renewable energy growth have stated publicly and privately that his analyses simply don’t add up, and even violate basic biophysical principles.

When not spinning out preposterous renewable energy models and suing other researchers, Jacobson makes the remarkable claim that nuclear energy is carbon-intensive, based on life-cycle analysis that among other analytical sleights of hand, assumes that the existence of nuclear energy results in nuclear warfare and hence includes the carbon content of the resulting mushroom clouds. Nevertheless, Jacobson has been celebrated as a visionary researcher by the National Academies and the American Meteorological Society, is regularly quoted authoritatively by outlets like the New York Times, and showered with philanthropic dollars by Leonardo DiCaprio, Mark Ruffalo, and other benefactors.

Over the last 15 years, Jacobson and a handful of other academics and advocates have produced hundreds of technical-seeming analyses purporting to demonstrate that a hypothetical future powered entirely by existing renewable energy technologies is close at hand. With these promises of solar inevitability in hand, environmental groups like Greenpeace, Friends of the Earth, and Riverkeeper waged campaigns against new and existing nuclear power plants, leading to the premature closure of Duane Arnold, Three Mile Island, Indian Point, among many other plants. Over the course of the 2010s, about 8.5 gigawatts of US nuclear capacity was shuttered, about enough to power the state of New Jersey or Virginia.

Finland Succeeds. Energiewende Chickens Come Home to Roost

One notable target of anti-nuclear solarmaxxers was Olkiluoto 3, a nuclear plant that began construction in Finland in 2005 and by 2013 was years behind schedule and billions of dollars over budget. Olkiluoto became a symbol of nuclear energy’s decadence. This was in contrast to Germany’s “energiewende,” a nationwide mission to replace fossil fuels and nuclear with wind and solar.

In 2013 we compared Finland’s investment in Olkiluoto with Germany’s enormous subsidies for solar generation, demonstrating that Olkiluoto would provide electricity at approximately a quarter of the cost per unit as solar would under energiewende subsidies. This became Exhibit A in the solarmaxxers’ case against Breakthrough. In a 2015 blog post titled “Nuclear will die. Solar will live,” Smith alluded to this analysis, claiming that Breakthrough typified “the anti-solar antipathy of the pro-nuclear crowd.”

Notably, we don’t hear so much about that analysis today. Olkiluoto 3 opened in 2023 and generates a quarter of Finland’s total electricity. At the time that we completed our analysis, Finland’s electricity system, which already had a lot of nuclear and hydro generation, was about half as carbon intensive as Germany’s. Today, it is 8 times lower. And Finland’s average industrial electricity prices are now about two-thirds lower than Germany’s.

Germany, meanwhile, mortgaged its energy future to Russia and its claims to climate leadership to domestic coal and lignite, both of which were necessary to keep the lights on and its solar dreams alive. Especially since Russia’s invasion of Ukraine, high energy costs and shortages have devastated Germany’s industrial base. Today, its political leaders acknowledge the huge economic cost of those decisions.

Neither this particular comparison nor Germany’s particularly zealous energy policies should suggest that solar power isn’t an important energy technology. We believed in solar back in 2013 and we still believe in it now. Notice that we never wrote that “solar will die and nuclear will live.”

But it is also important to note that even with the massive delays and cost overruns that solarmaxxers endlessly emphasize, nuclear power plants generate clean, affordable, and reliable electricity, with a tiny land footprint and secure supply chains, and will do so for 60 to 80 years or perhaps longer. Places like Finland that manage to build new reactors—even when they take longer than planned and cost more than anticipated—will benefit from cheap, clean electricity for the rest of this century.

That said, we have never been sanguine about the megaproject approach to nuclear power expansion. Even in Finland, a small country with a vertically integrated electric power system, it took many years and many more billions of dollars than originally envisioned to complete construction of Olkiluoto 3. A similar story played out with the Vogtle nuclear project, which also went considerably over deadline and over budget, even in Georgia’s vertically integrated market that allowed Southern Company to ratebase the plant’s construction.

Outside these cost-of-service markets—which is to say, in most of the United States—it’s even harder to finance construction of a multi-billion dollar commodity-producing megaproject. If this represents the future of nuclear energy, we are not likely to get very far with it. Large, conventional reactors will continue to have a role in places with the right political and institutional arrangements. But much as solar and wind cannot be the sole energy source powering a fast-growing global economy that needs electricity that is available all the time, conventional nuclear cannot be the sole pathway to expanding the role of nuclear power.

For this reason, we have focused our research and advocacy on the commercialization and deployment of a next generation of smaller reactors with different fuels and fuel cycles that will enable modular production, right-sizing power plants to varying geographies and customers, economies of scale and multiples, and other features to lower the costs of nuclear construction. In other words, our ambition as technology advocates has been to make the nuclear industry look a bit more like the solar industry.

Innovation vs. Forever Subsidies

One of the ironies about the intense reaction to our comparison of Finland and Germany was that despite the excessive cost of Germany’s solar subsidies, we supported them as innovation policy. The hundreds of billions of euros that Germany poured into its feed-in tariffs and other policies were both necessary to drive down solar costs and proof that it was, in fact, very expensive. The energiewende proved to be a fiscal, economic, and geopolitical disaster for Germany and demonstrated that attempting to power a modern, industrialized economy entirely with variable renewable energy is a terrible idea. But it has significantly benefitted the rest of the world.

Solarmaxxers during this period, by contrast, typically played a motte and bailey game, touting the ascendance of solar in Germany’s energy system as proof that it was cost effective and feasible at large scale and then retreating to an argument about its importance for innovation and the future of the energy system whenever anyone pointed out the extraordinary cost of the energiewende, Germany’s world leading electricity prices, or its curious dependence on coal.

Our view of Germany’s solar investments was consistent with our broader take on energy innovation. We championed solar subsidies in the US for well over a decade, in the face of critics from the Left who insisted that carbon caps and pricing had to be the central focus of climate policy and critics from the Right who argued that state support to commercialize new energy technologies amounted to “picking winners and losers,” because we believed that solar was a technology with enormous potential and that commercializing solar would require state support for a period of time.

Throughout those years, we insisted that public investments in nascent technologies were the historic norm, and that deployment subsidies to help drive down the cost of solar panels were an entirely appropriate clean energy policy. We also argued that deployment subsidies should be temporary as technologies like solar power achieved price parity with fossil fuels. As Jesse Jenkins and Tyler Norris wrote for Breakthrough in 2009, “we are proposing to use public investments in a highly specific and targeted way, at several defined points in the innovation process, in order to drive cost reductions in the unsubsidized price of clean energy technologies.”

That’s why, starting in 2020, we advocated that federal deployment tax credits for solar and onshore wind be phased down. Solar and wind had become mature, competitive industries. The point of the subsidies, we had always argued, was to achieve precisely this state of economic parity. More so than any energy technology save perhaps fracking, solar panels provided a positive proof point of the “make clean energy cheap” thesis that had made Breakthrough so controversial in the first place.

But the controversy didn’t end with solar’s success. At the onset of the Biden Administration, we advocated shifting federal clean technology supports towards less commercially mature technologies like advanced nuclear, deep-earth geothermal, and long-duration storage. The climate movement had other ideas and ultimately prevailed, passing hundreds of billions of dollars in expanded subsidies for solar and wind in the Inflation Reduction Act. In contrast to our solar optimism, solarmaxxers like Naam, despite their claims that solar is already the cheapest form of electricity in most places, continue to push for longer and larger subsidies.

It is slowly dawning on the more pragmatic quadrants of the climate movement what a mistake that was. Transforming once-bipartisan technology deployment tax credits into hyperpartisan emissions reduction subsidies polarized energy policy to an unprecedented degree, earning Democrats a bruising punishment in the form of Our Big Beautiful Bill only three years after the IRA’s passage. Spending hundreds of billions of inflation-juicing taxpayer dollars on an issue that, it turns out, the public doesn’t care very much about did not yield the political benefits climate hawks were counting on during the Biden years. As energy demand and interest rates have spiked, more and more researchers are recognizing the ways in which renewables subsidies—especially ratepayer subsidies for rooftop solar and state-level renewable energy mandates—are driving electricity prices upwards, not downwards.

And yet, even as federal subsidies sunset, solar power continues to expand impressively in the United States. Industry analysts expect annual solar deployments to decline somewhat after the expiration of the tax credits, but to remain nearly double 2020 rates each year through the end of the decade. And where solar and wind are not mandated by policy, they are associated with marginally lower power prices.

That’s because we solar optimists were right and the solarmaxxers were wrong. Solar power is an important, affordable, commercially mature technology that energy producers and consumers will now deploy for economic reasons without subsidies or mandates. What they will not do is rely on solar power for 100% of their energy system, even with the behind-the-meter and grid-scale battery storage technologies that have also come down significantly in cost.

Solar’s impressive success story is not a sign that it is “winning,” per se. The power grid has been and remains a mix of generation technologies. US natural gas generation, for instance, increased by over 300,000 MWhs from 2021 through 2024—approximately equal to total US solar generation in 2024. This is a complementary, not a competitive, relationship that we at Breakthrough have long observed.

The maturation of solar energy as a commercially viable energy technology, meanwhile, has not coincided with the death of nuclear. In fact, just the opposite: As electrification and power-hungry data centers are pushing US electricity demand up for the first time in a generation, large load customers are looking for electrons wherever they can get them. In some cases, that has meant investing in grid expansion and power purchase agreements for solar and battery storage. But there has been little appetite for behind-the-meter solar and batteries to power these loads. Rather, hyperscalers and other large load customers are betting on natural gas in the short term and clean, firm generation in the future, inclusive of new, existing, and restarted nuclear power plants, emergent geothermal, and natural gas with carbon removal technologies.

Against Energy Technology Fanaticism

Smith and Naam will surely tell you that they support all of these technologies, especially the low-carbon ones. As Smith wrote in his first inaccurate critique of Breakthrough over a decade ago, “Our government should continue to fund research into next-generation nuclear power.” Their problem with Breakthrough, purportedly, is not so much our nuclear advocacy as our perceived “anti-solar” bias. But as this history should establish, that perception is false.

We have not only been optimistic about solar but championed sensible policies to support solar and its deployment for twenty years. Even today, we most often find ourselves reassuring deflated climate hawks that solar and batteries can stand on their own two feet without subsidies, and that the Trump Administration’s various broadsides against renewables will not be enough to stop the solar train from chugging along.

So what is contested here is not whether solar energy has gotten very cheap, or whether IEA projections for solar and wind energy in 2010 or 2014 were accurate, or whether solar and wind are likely to grab significantly larger shares of global electricity generation in the coming decades. It is whether solar and wind can plausibly power most or all of the global economy, and whether betting the future of the energy economy and decarbonization solely on variable sources of renewable energy is a good idea.

Since our founding, we have argued that solar power merited special consideration in forecasts of a clean energy future. In 2015’s “An Ecomodernist Manifesto,” we called out solar and nuclear as the two technologies capable of achieving “the joint goals of climate stabilization and radical decoupling of humans from nature.” Even so, we have also supported ongoing oil and gas production in the United States, as well as public policies to support wind, geothermal, hydrogen, carbon removal technologies, electric vehicles, and other plausible complements to a future of energy abundance.

By contrast, and in somewhat different ways, both solarmaxxers like Smith and Naam and nuclearmaxxers such as our former colleague Michael Shellenberger are promoting extremely deterministic views of the energy system and its future. We would counsel both sides in this ancient feud that technological futures unavoidably involve deep uncertainty. Energy systems are both path-dependent and emergent. They are shaped by unpredictable macroeconomic and technological forces and by policy in both intended and unintended ways. Different energy technologies can both compete with and complement one another depending upon the context.

And so, more than a decade after first suggesting this to Smith, we would remind him, Naam, and all the solarmaxxers that wisdom and humility dictate that we hedge our energy technology bets. Neither solar nor nuclear is remotely on track to meet all of the world’s future energy needs any time soon. We are far more likely to succeed in building an abundant energy future if we pursue a broad portfolio of technologies and strategies rather than insisting fanatically upon a single technological solution.