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Just don’t confuse them with SMRs.
When politicians tell the CEO of Radiant that they love small modular reactors, he groans inwardly and just keeps smiling.
Doug Bernauer’s Radiant is not trying to make SMRs. His company — a VC-backed startup currently in the pre-application phase with the Nuclear Regulatory Commission — is designing a portable nuclear microreactor, which is intended to replace diesel generators. The politicians don’t always know the difference, Bernauer told me.
The SMR-microreactor confusion is common outside the world of nuclear. While they are both versions of advanced nuclear technologies not yet built in the United States (all of our nuclear power comes from big, old-fashioned plants), SMRs and microreactors have different designs, power outputs, costs, financing models, and potential use cases.
Unlike SMRs, microreactors are too small to ever become key energy players within a full-sized grid. But they could replace fossil fuels in some of the hardest to decarbonize sectors and locations in the world: mines, factories, towns in remote locations (especially Alaska and northern Canada), military bases, and (ironically) oil fields. For those customers, they could also make power supply and prices more consistent, secure, and dependable than fossil fuels, whose fluctuating prices batter industrial sectors and the residents of remote towns without discrimination.
Perhaps even more importantly, microreactors’ small size and comparatively low price could make them a gateway drug for new nuclear technologies in the U.S., helping companies and regulators build the know-how they need to lower the risk and cost for larger projects.
Heatmap Illustration/Radiant, IAEA, Getty Images
The big problem with this idea? No functional commercial nuclear microreactor actually exists. Industry experts cannot say with confidence that they know what the technological hurdles are going to be, how to solve them, or what it’s going to cost to address them.
“My crystal ball is broken,” John Parsons, an economist researching risk in energy at the Massachusetts Institute of Technology, said when I asked him whether he believed microreactors would make it through the technical gauntlet. “I’m hopeful. But I’m also very open-minded. I don’t know what’s going to happen. And I really believe we need a lot of shots on goal, and not all shots are going to go through,” he said.
Recent advances in both technology and regulation indicate that in the next few years, we should have some answers.
Private companies are expecting to conduct their first tests in about two years, and they are in conversations with potential customers. Radiant is hoping to test at the Idaho National Laboratory in 2026; Westinghouse and Ultra Safe Nuclear Corporation have contracts to test microreactors there as well. BWX Technologies is currently procuring the parts for a demonstration reactor through the Department of Defense’s prototype program — called Project Pele — and plans to test in about two years; X-energy signed an expanded contract in 2023 to build a prototype for Project Pele as well. Eielson Air Force Base in Alaska is commissioning a pilot microreactor. Schools including Pennsylvania State University and the University of Illinois have announced their interest as potential customers. Mining companies and other industry players in Alaska regularly express interest in embracing this technology.
The government is also quietly smoothing the way, removing barriers to make those tests possible. On March 4, the Nuclear Regulatory Commission released a new draft of licensing rules that will shape the future for these microreactors, and early March’s emergency spending bill included more than $2.5 billion repurposed for investment in a domestic supply chain of the type of nuclear fuel most advanced reactors will require.
“If we are truly committed as a nation to sticking to our climate goals, then we will absolutely get to a place where there are a bunch of microreactors replacing otherwise difficult to decarbonize sectors and applications,” said Kathryn Huff, the head of the office of nuclear energy at the Department of Energy.
Eric Gimon, a senior fellow at the nonprofit Energy Innovation, was a microreactor skeptic until about a month ago. His own recent research has made him far more optimistic that these microreactors might actually be technologically feasible, he told me when I reached out for an honest critique. “If they can make (the microreactors) work, it’s attractive,” he said. “There are a lot of industrial players that are going to want to buy them.”
“If your goal is to produce power at 4 cents per kilowatt hour, why would you buy any power that’s way more expensive than what you need? You do it because if that adds diversity to the portfolio and less variance, then you can get an overall portfolio that is lower cost or a lower risk for the same cost,” he told me.
Everyone I spoke to in the industry began our conversation with the same analogy: In the world of nuclear, full-size power plants are to airports what microreactors are to airplanes. Just as it's easier to build and regulate an airplane than an entire airport, in theory the microreactors should be built in a factory, regulated and licensed in the factory, and then rented out to or sold to the end user. An airport requires approvals specific to the construction site, a huge team of people employed for a long time to construct it and then another team to maintain it, and complicated financing based on the idea that the airport could be used for 50 or more years; a full-scale nuclear plant is the same. An airplane can basically be ordered online; a microreactor should be the same.
“They are sized to be similar to that kind of scope, where you could really consolidate a lot of the chemical and manufacturing oversight to a single location rather than moving thousands of people to a construction site,” Huff told me.
Microreactors should produce relatively small amounts of power (a maximum of 10-20 megawatts) and lots of heat with a tiny amount of nuclear fuel. They are usually portable, and if they aren’t portable they require a limited amount of construction or installation. Because it should not be possible to handle the fuel once it leaves the factory (most of the proposed reactor designs set the fuel deep into a dense, inaccessible matrix), these reactors wouldn’t require the same safety and security measures on site as a nuclear power plant. They’re easily operated or managed by people without nuclear expertise, and their safety design — called passive safety — should make it technically impossible for a reactor to meltdown.
“The excess reactivity is so small that you actually can’t get the reactor hot enough that you could start damaging the fuel. That’s something unique about the microreactor that would not necessarily be true for other types of nuclear,” Jeff Waksman, the program manager for the Department of Defense’s Strategic Capabilities Office, told me.
Microreactors should also cost on the order of tens of millions of dollars, not hundreds. That’s low enough that a company, university, town, or other similarly-sized entity could buy one or more of them. Because they’re cheaper than traditional nuclear, they don’t require lenders to take big risks on money committed over a very long period of time. If a mining company wanted to replace a diesel generator with one of these, they should be able to finance it in exactly the same way (a loan from the bank, for example). This makes their financial logic quite different from SMRs, which can suffer from some of the same problems as full-size nuclear power plants (see: NuScale’s recent setbacks).
“All of the things that contribute to a faster innovation cycle are true for microreactors compared to larger reactors. So you can just — build one,” said Rachel Slaybaugh, a partner at DCVC and a board member at Radiant, Fervo Energy, and Fourth Power.
Because microreactors max out at around 20 megawatts of energy, the economies of scale that eventually bring down energy prices for full-scale nuclear power can’t be replicated. While Jigar Shah, the director of the loan programs office at the DOE, speculated in a recent interview that costs might eventually go just below 10 cents per kilowatt hour, Parsons is skeptical that anyone could provide a practical cost estimate. It’s absolutely going to cost more than either large reactors or SMRs, Parsons said.
But cost comparisons to other types of nuclear technology aren’t practical, according to Slaybaugh. “You are going to be able to command a cost parity with diesel generators. It’s easy to get to a point where they make financial sense,” she said. “You can see why someone would pick one: This is not making noise, it’s not making local air pollution, you don’t have to deal with the diesel logistics complexity. You sell it at price parity, and maybe the first few customers pay a premium because they are excited about it.”
That premium price for the initial technology is the largest hurdle raised by every single person I spoke with, from the DOE to analysts and researchers to the different microreactor companies.
But there is one customer already inclined to pay a substantial premium: the Department of Defense. The U.S. military has greater resiliency and security needs than other consumers when it comes to its power supply, making the cost of microreactors more palatable. (And it doesn’t hurt that the taxpayer already foots the bill for enormous defense contracts, including for aircraft carriers and submarines powered by nuclear reactors). It’s common for technological innovations (think the internet, GPS, advanced prosthetics) to begin with the military and then expand outward to the consumer. Project Pele and the requests for proposals at Eielson Air Force Base both indicate that the pathway might be one for microreactors, according to Parsons.
For the president of BWXT Advanced Technologies, the Department of Defense’s decision to commission his company’s microreactor for Project Pele removed his last doubts that these microreactors would eventually be built. “The DOD being the first mover has extreme advantage for the country, and for eventually the commercial industry,” Joseph Miller told me. “The first mover was the barrier, and now it’s just 1,000 things that we’re working on all day every day to make it real, and there’s no gotcha out there that I see. That wasn’t the case when we were doing the design work, but now we’re making procurements to be able to assemble and deliver the reactor.”
Regardless of whether Miller’s optimism is well-founded, the experience gained in trying to make them happen is invaluable for a nuclear industry that’s been stuck in the mud for far too long.
“I've been talking with the federal government about the fact that there’s broader value in terms of getting wins on the board for the nuclear sector and getting the industry more experienced with building new things in a way that isn't quite so complicated,” Slaybaugh said. “Let’s have them build a thing that’s small and kind of cheap, and then they can go build a bigger thing that’s a little more expensive and a little more complicated. Let’s get some real reps in with microreactors.”
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Investing in red states doesn’t make defying Trump any safer.
In the end, it was what the letters didn’t say.
For months — since well before the 2024 election — when asked about the future health and safety of the clean energy tax credits in the Inflation Reduction Act, advocates and industry folks would point to the 20 or so House Republicans (sometimes more, sometimes fewer) who would sign on to public statements urging their colleagues to preserve at least some of the law. Better not to pull out the rug from business investment, they argued. Especially not investment in their districts.
These letters were “reassuring to a lot of folks in clean energy and climate communities,” Chris Moyer, the founder of Echo Communications and a former staffer for longtime Senate Majority Leader Harry Reid, told me.
“I never felt reassured,” Moyer added.
Plenty of people did, though. The home solar company Sunrun, for instance, told investors in a presentation earlier this monththat a “growing number of Republicans in Congress — including 39 overall House members and four Senators — publicly support maintaining energy tax credits through various letters over the past few months.” The company added that “we expect a range of draft proposals to be issued, possibly including draconian scenarios, but we expect any extreme proposals will be moderated as they progress.”
Instead, the draft language got progressively worse for the residential solar industry, with the version that passed the House Thursday morning knocking billions of dollars off the sector, as tax credits were further squeezed to help make room for other priorities that truly posed an existential threat to the bill’s passage.
What Sunrun and others appear to have failed to notice — or at least publicly acknowledge — is that while these representatives wanted to see tax credits preserved, they never specified what they would do if their wishes were disregarded. Unlike the handful of Republicans who threatened to tank the bill over expanding the deduction for state and local taxes (each of whom signed one of the tax credit letters, at some point), or the Freedom Caucus, who tend to vote no on any major fiscal bill that doesn’t contain sizable spending cuts (so, until now, every budget bill), the tax credit Republicans never threatened to kill the bill entirely.
Ultimately, the only Republicans to outright oppose the bill did so because it didn’t cut the deficit enough. All of the House Republicans who signed letters or statements in support of clean energy tax credits voted yes on the legislation, with a single exception: New York’s Andrew Garbarino, who reportedly slept through the roll call. (He later said he would have voted for it had he been awake.)
“The coalition of interests effectively persuaded Republican members that tax credits were driving investment in their districts and states,” Pavan Venkatakrishnan, an infrastructure fellow at the Institute for Progress, told me in a text message. “Where advocates fell short was in convincing them that preserving energy tax credits — especially for mature technologies Republicans often view skeptically — should take precedence over preventing Medicaid cuts or addressing parochial concerns like SALT.”
The Inflation Reduction Act itself was, after all, advanced on a party-line basis, as was Biden’s 2021 American Rescue Plan. Combined, those two bills received a single Democratic no vote and no Republican yes votes.
In the end, Moyer said, Republican House members in the current Congress were under immense political pressure to support what is likely to be the sole major piece of legislation advanced this year by President Trump — one that contained a number of provisions, especially on SALT, that they agreed with.
“There are major consequences for individual house members who vote against the president’s agenda,” Moyer said. “They made a calculation. They knew they were going to take heat either way. They would rather take heat from clean energy folks and people affected by the projects.”
It wasn’t supposed to be this way.
White House officials and outside analysts frequently touted job creation linked to IRA investments in Republican House districts and states as a tangible benefit of the law that would make it politically impossible to overturn, even as Congress and the White House turned over.
“President’s Biden’s policies are leading to more than 330,000 new clean energy jobs already created, more than half of which are in Republican-held districts,” White House communications director Ben LaBolt told reporters last year, previewing a speech President Biden would give on climate change.
Even after Biden had been defeated, White House climate advisor Ali Zaidi told Bloomberg that “we have grown the political consensus around the Inflation Reduction Act through its execution,” citing one of the House Republican letters in support of the clean energy tax credits.
One former Biden White House climate official told me that having projects in Republican districts was thought by the IRA’s crafters to make the bill more politically sustainable — but only so much.
“A [freaking] battery factory is not going to save democracy,” the official told me, referencing more ambitious claims that the tax credits could lead to more Democratic electoral victories. (The official asked to remain anonymous in order not to jeopardize their current professional prospects.) Instead, “it was supposed to make it slightly harder for Republicans to overturn the subsidies.”
Congresspeople worried about jobs weren’t supposed to be the only things that would preserve the bill, either, the official added. Clean energy and energy-dependent sectors, they thought, should be able to effectively advocate for themselves.
To the extent that business interests were able to win a hearing with House Republicans, they were older, more traditionally conservative industries such as nuclear, manufacturing, agriculture, and oil and gas.The biofuels industry (i.e. liquid Big Agriculture) won an extension of its tax credit, 45Z. The oil and gas industry’s favored measure, the 45Q tax credit for carbon sequestration, was minimally fettered. Nuclear power was the one sector whose treatment notably improved between the initial draft from the House’s tax-writing committee and the version voted on Thursday. Advanced nuclear facilities can still claim tax credits if they start construction by 2029, while other clean energy projects have to start construction within 60 days of the bill’s passage and be in service by the end of 2028.
“I think these outcomes are unsurprising. In places where folks consistently engaged, things were protected,” a Republican lobbyist told me, referring to manufacturing, biofuels, and nuclear power, requesting anonymity because they weren’t authorized to speak publicly. “But assuming a project in a district would guarantee a no vote on a large package was always a mistake.”
“The relative success of nuclear is a testament to the importance of having strong champions — predictable but notable show of political might,” a second Republican lobbyist told me, who was also not allowed to speak publicly about the bill.
But all hope isn’t lost yet. The Senate still has to pass something that the House will agree with. Some senators had made noises about how nuclear, hydropower, and geothermal were treated in the initial language.
“Budget reconciliation is, first and foremost, a fiscal exercise,” Venkatakrishnan told me. “Energy tax credits offer a path of least resistance for hitting lawmakers’ fiscal targets. As the Senate takes up this bill, the case must be made that the marginal $100 billion to $200 billion in cuts seriously jeopardizes grid reliability and energy innovation.” Whether that will be enough to generate meaningful opposition in the Senate, however, is the $600 billion question.
A loophole created by the House Ways and Means text disappeared in the final bill.
Early this morning, the House of Representatives launched a full-frontal assault on the residential solar business model. The new language in the budget reconciliation bill to extend the Tax Cuts and Jobs Act passed Thursday included even tighter restrictions on the tech-neutral investment tax credits claimed by businesses like Sunrun when they lease solar systems to residential buyers.
While the earlier language from the Ways and Means committee eliminated the 25D tax credit for those who purchased home solar systems after the end of this year (it was originally supposed to run through 2034), the new language says that no credit “shall be allowed under this section for any investment during the taxable year” (emphasis mine) if the entity claiming the tax credit “rents or leases such property to a third party during such taxable year” and “the lessee would qualify for a credit under section 25D with respect to such property if the lessee owned such property.”
This is how you kill a business model in legislative text.
“Expect shares of solar companies to take a significant step back,” Jefferies analyst Julien Dumoulin-Smith wrote in a note to clients Thursday morning, calling the exclusion “scathing.” Investors are “losing the now false sense of security that we had 'seen the worst' of it with the initial House draft.”
Joseph Osha, an analyst for Guggenheim, agrees. “Considering the fact that ~70% of the residential solar industry is now supported by third-party (e.g. lease or PPA) financing arrangements, the new language is disastrous for the residential solar industry,” he wrote in a note to clients. “We believe the near-term implications are very negative for Sunrun, Enphase, and SolarEdge.”
Shares of Sunrun are down 37.5% in mid-day trading, wiping off almost $1 billion worth of value for its shareholders. The company did not respond to a request for comment. Shares of fellow residential solar inverter and systems Enphase are down 20%, while residential solar technology company SolarEdge’s shares are down 24.5%.
“Families will lose the freedom to control their energy costs,” Abigail Ross Hopper, chief executive of the Solar Energy Industries Association, said in a statement, in reference to the last-minute alteration to the investment tax credit.
When the House Ways and Means Committee released the initial language getting rid of 25D by the end of this year but keeping a limited version of the investment tax credit, analysts noted that Sunrun was an unexpected winner from the bill. It typically markets its solar products as leases or power purchase agreements, not outright sales of the system.
The reversal, Dumoulin-Smith wrote, “comes as a surprise especially considering how favorable the initial markup was” to the Sunrun business model.
“Our core solar service offerings are provided through our lease and power purchase agreements,” the company said in its 2024 annual report. “While customers have the option to purchase a solar energy system outright from us, most of our customers choose to buy solar as a service from us through our Customer Agreements without the significant upfront investment of purchasing a solar energy system.”
The new bill, Dumoulin-Smith writes is “‘leveling the playing field’ by targeting all future residential solar originations, whether leased or owned.” The bill is “negative to Sunrun with intentional targeting of the sector.
Last year, Sunrun generated over $700 million from transferring investment tax credits from its solar and storage projects. The company said that it had $117 million of “incentives revenue” in 2024, which includes the tax credits, out of around $1.4 billion in total revenue.
But the tax credits play a far larger role in the business than just how they’re recognized on the company’s earnings statements. The company raises investment funds to help finance the projects, where investors get payments from customers as well as monetized tax credits. Fund investors “can receive attractive after-tax returns from our investment funds due to their ability to utilize Commercial ITCs,” the company said in its report. Conversely, the financing “enables us to offer attractive pricing to our customers for the energy generated by the solar energy system on their homes.”
Morgan Stanley analyst Andrew Perocco wrote to clients that “this is a noteworthy change for the residential solar industry, and Sunrun in particular, which dominates the residential solar [third-party owned] market and has recognized ITC credits under 48E.”
Current conditions: A late-season nor’easter could bring minor flooding to the Boston area• It’s clear and sunny today in Erbil, Iraq, where the country’s first entirely off-grid, solar-powered village is now operating • Thursday will finally bring a break from severe storms in the U.S., which has seen 280 tornadoes more than the historical average this year.
1. House GOP passes reconciliation bill after late-night tweaks to clean energy tax credits
The House passed the sweeping “big, beautiful” tax bill early Thursday morning in a 215-214 vote, mostly along party lines. Republican Representatives Thomas Massie of Kentucky and Warren Davidson of Ohio voted no, while House Freedom Caucus Chair Andy Harris of Maryland voted “present;” two additional Republicans didn’t vote.
The bill will effectively kill the Inflation Reduction Act, as my colleague Emily Pontecorvo has written — although the Wednesday night manager’s amendment included some tweaks to how, exactly, as well as a few concessions to moderates. Updates include:
The bill now heads to the Senate — where more negotiations will almost certainly follow — with Republicans aiming to have it on President Trump’s desk by July 4.
2. FEMA cancels 4-year strategic plan, axing focus on ‘climate resilience’
The combative new acting administrator of the Federal Emergency Management Agency, David Richardson, rescinded the organization’s four-year strategic plan on Wednesday, per Wired. Though the document, which was set to expire at the end of 2026, does not address specific procedures for given disasters, it does lay out goals and objectives for the agency, including “lead whole of community in climate resilience” and “install equality as a foundation of emergency management.” In axing the strategic plan, Richardson told staff that the document “contains goals and objectives that bear no connection to FEMA accomplishing its mission.”
A FEMA employee who spoke with Wired stressed that while rescinding the plan does not have immediate operational impacts, it can still have “big downstream effects.” Another characterized the move by the administration as symbolic: “There are very real changes that have been made that touch on [equity and climate change] that are more important than the document itself.”
3. Energy Department redirects Puerto Rican rooftop solar investment to upkeep of fossil fuel plants
The U.S. federal government is redirecting a $365 million investment in rooftop solar power in Puerto Rico to instead maintain the island’s fossil fuel-powered grid, the Department of Energy announced Wednesday. The award, which dates to the Biden administration, was intended to provide stable power to Puerto Ricans, who have become accustomed to blackouts due to damaged and outdated infrastructure. The Puerto Rico Electric Power Authority declared bankruptcy in 2017, and a barrage of major hurricanes — most notably 2017’s Hurricane Maria — have destabilized the island’s grid, Reuters reports.
In Energy Secretary Chris Wright’s statement, he said the funds will go toward “dispatching baseload generation units, supporting vegetation control to protect transmission lines, and upgrading aging infrastructure.” But Javier Rúa Jovet, a public policy director for Puerto Rico’s Solar and Energy Storage Association, added to The Associated Press that “There is nothing faster and better than solar batteries.”
4. EDF, Shell, and others to collaborate on hydrogen emission tracker
The Environmental Defense Fund announced Wednesday that it is launching an international research initiative to track hydrogen emissions from North American and European facilities, in partnership with Shell, TotalEnergies, Air Products, and Air Liquide, as well as other academic and technology partners. Hydrogen is an indirect greenhouse gas that, through chemical reactions, can affect the lifetime and abundances of planet-warming gases like methane and ozone. Despite being a “leak-prone gas,” hydrogen emissions have been poorly studied.
“As hydrogen becomes an increasingly important part of the energy system, developing a robust, data-driven understanding of its emissions is essential to supporting informed decisions and guiding future investments in the sector,” Steven Hamburg, the chief scientist and senior vice president of EDF, said in a statement. Notably, EDF took a similar approach to tracking methane over a decade ago and ultimately exposed that emissions were “a far greater threat” than official government estimates suggested.
5. The best-selling SUV in America will now be available only as a hybrid
Toyota
The bestselling SUV in America, the Toyota RAV4, will be available only as a hybrid beginning with the 2026 model, Car and Driver reports. The car will be available both as a conventional hybrid and as a plug-in that works with CCS-compatible DC fast chargers, meaning “owners can quickly fill up its battery during long road trips” to minimize their fossil fuel mileage, The Verge adds. The RAV4 will also beat the Prius for electric range, hitting up to 50 miles before its gas engine kicks in.
Toyota’s move might not come as a complete surprise given that the automaker already introduced a hybrid-only lineup for its Camry. But given the popularity of the RAV4, Car and Driver notes that “if you ever wondered whether or not hybrids have entered the mainstream yet, perhaps this could be a tipping point.”
Nathan Hurner/USFWS
The Fish Lake Valley tui chub, a small minnow threatened by farming and mining activity, could become the first species to be listed as endangered under the second Trump administration.