Fusion power might not get cheap as fast as you think

Fusion power has this almost mythical aura around it — clean, limitless, zero-emissions electricity that could solve our energy problems. But a new study from researchers at ETH Zurich pours some cold water on the hype. Even if we get fusion plants built and running, they might not be cheap.

We’re used to tech getting cheaper over time. Lithium-ion batteries are about 90% cheaper than they were in 2013. Solar modules have followed a similar trajectory. But not everything follows that curve at the same pace, and fusion might be one of the slow ones.

The key metric here is something called the experience rate — the percentage by which a technology’s cost drops every time its global installed capacity doubles. Solar modules have an experience rate of 23%. Lithium-ion batteries sit at 20%. Onshore wind is around 12%. Nuclear fission? A paltry 2%.

Now, predicting costs for a technology that doesn’t actually exist yet is inherently tricky. But with billions of dollars on the line — the US allocated over $1 billion to fusion in fiscal 2024, and private funding hit $2.2 billion between July 2024 and July 2025 — it’s worth asking what assumptions we’re making.

The researchers behind the new paper, published in Nature Energy, tried to estimate fusion’s experience rate by looking at three factors that historically correlate with how fast a technology gets cheaper: unit size, design complexity, and how much customization it needs. The bigger, more complex, and more customized something is, the slower its cost declines.

They interviewed fusion experts — both public-sector researchers and folks at private companies — and had them rate fusion power plants on those characteristics. The results weren’t great. Fusion plants will likely be large, similar to coal or fission plants. They’ll need less customization than fission (regulations should be simpler), but more than something like solar panels. And complexity? “There was almost unanimous agreement that fusion is incredibly complex,” says Lingxi Tang, a PhD candidate at ETH Zurich and one of the study’s authors. Some experts said it was literally off the scale the researchers gave them.

The final estimate: fusion’s experience rate falls somewhere between 2% and 8%. That’s better than fission, but nowhere near the 8% to 20% that many modeling studies currently assume. It means we’d need a lot of deployment — and a lot of time — before building a fusion reactor becomes cheap. Electricity from fusion plants could stay expensive for a long while.

Tang doesn’t mince words: “On the whole, I think questions should be raised about current investment levels in fusion.” He asks whether this is really the best use of public money if we’re serious about decarbonizing the energy system.

But not everyone agrees that looking backward tells us much about the future. Egemen Kolemen, a professor at Princeton Plasma Physics Laboratory, points out that in 2000, many analysts predicted solar would stay expensive. Then China went all in, production exploded, and prices crashed. “People weren’t exactly wrong then,” he says. “They were just extrapolating what they saw into the future.”

His point is fair: how fast prices drop depends on regulations, geopolitics, and labor costs — things you can’t model from historical data alone. “We haven’t built the thing yet, so we don’t know,” he says.

So where does that leave us? Fusion could still be a game-changer, but the timeline and the price tag are more uncertain than the hype suggests. If you’re betting on fusion to save us, you might want to hedge your bets with technologies that are already getting cheaper today.