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X-energy's halved shares test the exits behind nuclear's record $6 billion funding year
Investors have put more than $6 billion into nuclear fission and fusion startups in 2026, a record by Crunchbase's count. The IPO market those investors would one day sell into has marked most recent nuclear listings far below their peaks.
The Investor · Invest desk
What happened
- Commonwealth Fusion Systems raised $1 billion in a July equity round and Valar Atomics $1 billion over two Series B tranches, together a little under a third of the year's total.
- X-energy, the largest recent nuclear listing, hit a $12 billion valuation in its first trading in April and has since lost about half its value.
- Oklo, whose 2024 SPAC debut started the run of nuclear listings, trades about two-thirds below a high it reached roughly a year ago.
- Crunchbase says the number of nuclear funding rounds is also holding at historically high levels, so the money is not confined to the two largest deals.
Compiled by The InvestorSomething wrong?How this is made
Why it matters
- exposure One listed stock, X-energy, has lost about $6 billion of market value, roughly what private investors put into the whole sector this year, and later-stage backers of Commonwealth Fusion and Valar would exit into that market.
- constraint Oklo would have to triple and X-energy double to regain their highs, so the next nuclear startup to file will be priced beside listed peers still well below their peaks.
- exposure Crunchbase links the funding to AI power demand and part of the investor caution to backlash against data-center buildouts, so the bull case and the selloff depend on the same customers.
A first-day valuation and a $1 billion private round are both prices. Neither says much about value in a sector where, as Crunchbase notes, scalable fusion has yet to come online [12]. The report does not include the valuations attached to the Commonwealth Fusion Systems or Valar Atomics rounds [3][4], so the only nuclear marks anyone can check daily are the listed ones [5].
Crunchbase says it is unclear whether the declines in those listed shares reflect doubts about feasibility or a sense that valuations needed cutting [9]. The two lead to different places. A valuation cut leaves the companies building, with private rounds taking a haircut whenever they list. Doubt about feasibility brings in the EIA's base rate: very little US nuclear capacity built in decades, held back by high capital costs and long licensing and approval processes [11]. A third outcome runs the other way, if the small modular reactor and microreactor projects the EIA lists in Texas, Idaho, Utah and Tennessee start delivering and the listed names recover [13].
I think the valuation cut fits the evidence better. Private investors are still writing nuclear rounds at a historically high count, per Crunchbase [2], and investors who doubted the physics would be writing fewer. The counter is that private marks tend to move later than listed shares, so a steady count may only mean the markdown has not reached private books yet.
If the valuation reading is right, the funded companies have little reason to list soon. Crunchbase says this year's IPO and venture money has given startups the runway to keep going [14]. A company with that runway can wait out a market that has halved X-energy [6]. The holders of the more than $6 billion raised this year wait with it [1].
A nuclear IPO that prices above its issuer's last private round and holds there would show the public discount has closed. It would also show I have this wrong.
What to watch
- Whether X-energy's shares recover toward their $12 billion first-day valuation or keep falling, since every new nuclear filing will be priced beside them.
- The next nuclear IPO filing, and whether its price clears the issuer's last private round.
- First power, or schedule slips, at the small modular reactor and microreactor projects in Texas, Idaho, Utah and Tennessee.