What If We Get Fusion — But Don’t Need It?

Nuclear fusion, sometimes breathlessly referred to as the “holy grail” of clean energy, capable of providing “near limitless” energy, might actually, finally be on the verge of working. And when that first prototype reactor turns on, the feverish headlines about harnessing the power of the sun and the stars here on Earth will at least be somewhat justified. Fusion is going to be a massive scientific achievement, but in a practical sense, it might not matter.

“We can make it work,” Egemen Kolemen, fusion expert and associate professor of mechanical and aerospace engineering at Princeton University, told me. “But at what price?”

Figuring out fusion is one thing, penciling out the economics another. There’s a nontrivial chance that fusion could become a scientific reality but remain too expensive to make a dent in the barriers to decarbonization.

How this plays out largely depends on what the grid looks like by the mid-2030s, when the leading fusion startups think we’ll see the first demonstration reactors come online. President Biden wants to fully decarbonize the electricity sector by 2035. And as ambitious — or, as many say, unrealistic — as that may be, how close we get and how we get there will determine what opportunities remain for fusion.

By the mid-2030s, the cost of building new fission reactors could come down significantly; if The Nuclear Company has its way, we’ll have built a 6 gigawatt fleet of standard nuclear plants by then. Or maybe small, modular reactors will finally prove out, squeezing much of the market space for fusion. And then there’s all the other emergent, grid-firming tech in various stages of development. Think long-duration battery storage, enhanced geothermal, and hydrogen for starters.

“Batteries go down in price, hydrogen goes down, you know, two orders of magnitude, whatever. And then you say, we’re okay, we don’t need an extra [energy] source,” Kolemen told me. “So we have to be very clear that that’s an option as well.”

Needless to say, investors know it’s a gamble. “This is venture, of course there’s a chance that it might not be economically feasible,” Gabriel Kra, managing director and co-founder at climate tech VC Prelude Ventures, told me. “That’s not a reason, in any case, not to try.” Prelude Ventures has invested in two fusion companies, Thea Energy and Xcimer Energy, while venture capitalists on the whole have poured $6.7 billion into fusion since 1992, according to the Fusion Industry Association, the vast majority of that in the past three years.

Many of these same venture firms are also placing big bets on other energy solutions that promise to provide many of the same benefits as fusion, such as Fervo’s enhanced geothermal tech, or Koloma’s artificial intelligence-powered geologic hydrogen detection system, or Form Energy’s long-duration iron-air batteries. But because none of these brand new technologies has yet achieved meaningful scale, creating simple price forecasts or cost curve models isn’t possible.

A refrain I heard a few times, however, is that no matter the energy mix of the future, fusion’s viability isn’t simply a matter of dollars and cents. “Even if fusion doesn’t get as cheap as solar or wind, or even if it doesn’t get as cheap as natural gas, there’s still a huge place for it in the grid,” Kra said.

Siting fusion reactors near dense urban areas, for example, could help solve one of the principal issues with renewables. “Even now, it’s becoming difficult to find sites for solar and wind, and we have a fraction of what we would need,” Jacob Schwartz, a staff research physicist at the Princeton Plasma Physics Laboratory, told me. “If you really want a lot of firm power that can be much physically denser than these other resources, you might really want to build fusion.” Siting fusion next to demand centers would also reduce the need to permit and build long transmission lines, which can take a decade or more if it happens at all.

Of course, fission reactors have these advantages too. A paper Schwartz and Kolemen published last year, modeling fusion’s place in various net-zero grid scenarios from 2036 to 2050, found that in most of them, fusion plants would be primarily displacing fission. That is, if they made sense at all. The authors (including Princeton energy systems professor and Heatmap contributor Jesse Jenkins) also found that if the price of competing technologies creates at least a moderate market opportunity for fusion, we could wind up with 100 gigawatts or more of fusion capacity, about the size of the current domestic fission fleet. But if other technologies outperform and drop significantly in price, it’s possible that no commercial fusion plants would get built in that timeframe.

Kra, however, disagrees with a core assumption of the paper — that the U.S. will actually meet our carbon-free energy targets. “I don’t want to be a doomer, but I don’t think we’re going to decarbonize the grid by 2035,” Kra told me. “I think the first fusion plant that comes online, maybe between 2035 and 2040, will be displacing a fossil source at that moment in time.”

Looked at that way, the calculus changes. Fusion could become just another player in the renewables mix, slotting in alongside a plethora of other emergent and established carbon-free technologies to supplant fossil fuels in an all-of-the-above march towards zero emissions. It would still need to be cost-effective, of course, but if it’s framed as a possible successor to fossil fuels as opposed to a rival of existing clean energy sources, that’s a much better sales pitch.

That said, it’s going to take more than just reaching cost-parity with fission for fusion to take off. If that’s all we do, Kolemen told me, “it will have the exact same result, which is that nothing is going to be built.”

And even if fusion doesn’t end up penciling out for the U.S. grid, it may still in other areas of the world with less abundant renewable energy resources and rapid load growth. Phil Larochelle, the leader of Breakthrough Energy Ventures fusion investment strategy, told me that it’s really not the West that stands to benefit the most.

“You’ve got the rest of the world — call it, 80% of the world's population — who are trying to live a life of prosperity, like we do here.” But raising standards of living around the world means a huge increase in energy consumption. “And so then the question is, can you just kind of sneak across the finish line with wind, solar, storage, transmission, geothermal, a bit of natural gas?” Larochelle asked. While he said it should be possible, it wouldn’t allow for the flourishing vision of the future that he hopes to see. “Sustainable abundance for all. That’s, I think, where fusion really shines,” he told me.