Clean energy VC is no longer booming—but it is maturing.

According to PitchBook’s Q2 2025 data, overall clean energy VC deal value dropped 6% from Q1 and is on track for a second consecutive annual decline.

Yet beneath the surface, important shifts are taking place:

🧠 Fewer deals, bigger bets

The number of deals is down 22% year-over-year, but median deal sizes have jumped 65%. Investors are concentrating their firepower, targeting nuclear, grid software, and datacenter-friendly energy tech.

⚛️ VCs’ can’t get enough of Nuclear

Four of the seven largest deals this quarter went to nuclear startups. TerraPower raised $650M, with Nvidia’s VC arm participating. Fusion spinouts like Proxima Fusion and TAE also closed large rounds, riding the AI infrastructure wave.

📉 Solar, wind and lithium cooling off

Segments like solar PV, lithium-ion, and (finally!) green hydrogen saw steep drops in deal volume and value. Wind was the only intermittent segment with any notable momentum—led by startups like PhysicsX and Aerones.

🌐 Grid infrastructure is the new darling

With interconnection delays plaguing every market, investment in analytics, VPPs, and non-lithium batteries is rising fast. Base Power, Mainspring, and Natron are examples of this shift toward grid-enabling tech.

🏛️ Policy uncertainty casts a shadow

In the U.S., the rollback of IRA tax credits and sourcing rules introduced by the “One Big Beautiful Bill Act” are shaking confidence in solar and wind. Developers are rushing to meet revised deadlines—but exits remain weak.

So while the capital tide has receded, the strong swimmers are clearer now. Nuclear and grid tech are getting the spotlight.

Grid investments are long overdue, and I applaud their resurgence. VCs' fascination with nuclear puzzles me. Any investment in nuclear should have an investment horizon of 20+ years. Last time I checked, VCs aimed for 10 years at most.

An investment by the government or a big strategic investor would not have elicited any comments on my part, but with so much VC money thrown down the reactor core, we are witnessing the birth of another bubble.

For more on investment in nuclear energy, check out my dedicated blog section here.