U.S. climate tech startups raised $934M across 14 announced Series B funding events in the first quarter of 2026. 12 of these were milestone Series B rounds and 2 were extensions, second closes, etc.
Key takeaways:
- Series B dollars held roughly flat year over year. Companies raised $934M, about even with $916M a year ago, but up sharply from $371M in Q4 ’25. 12 milestone rounds (excludes extensions, bridges, etc), down from 14 in Q1 2025 and up from 10 last quarter.
- Energy took just over half, but was highly concentrated. Energy companies accounted for $537M, about 58% of Series B dollars, driven by EnerVenue’s $300M extension and Heron Power’s $140M round. But just 2 of the 12 milestone rounds were in Energy.
- A few large rounds carried the quarter. EnerVenue’s $300M extension and JetZero’s $175M round were the two biggest, together about half of all Series B dollars. The median milestone round was $60M.
The headline numbers
| Metric | Q1 2026 |
|---|---|
| Total Series B raised | $934M |
| Milestone rounds | 12 |
| Average milestone round | $67.0M |
| Median milestone round | $60.0M |
How Q1 compares
Quarter over quarter (vs Q4 2025): Series B dollars rose about 151%, from $371M to $934M, while milestone rounds rose from 10 to 12. The average round grew from $32.5M to $67.0M, and the median from $27.5M to $60.0M.
Year over year (vs Q1 2025): dollars were about flat, up 2% from $916M, while milestone rounds fell from 14 to 12. The average a year ago was $53.7M.
The two comparisons tell different stories. Year over year, Series B was about flat. The jump is against Q4 2025, which was a quiet quarter for the stage. Bigger rounds and a higher median this quarter point to capital concentrating in fewer, larger deals.
Where the money went
Energy led again, with the rest spread across five other verticals. One of our seven verticals (Carbon) saw no U.S. Series B activity this quarter.
| Vertical | Series B $ | Share | Milestone rounds |
|---|---|---|---|
| Energy | $537.0M | 58% | 2 |
| Transportation | $175.0M | 19% | 1 |
| Food & Land Use | $70.0M | 7% | 2 |
| Built Environment | $65.0M | 7% | 3 |
| Industry | $60.2M | 6% | 3 |
| Climate Management | $26.3M | 3% | 1 |
By technology type, physical plays took 97% of Series B dollars ($907M) and digital took just 3% ($26M). The one biotech round of the quarter closed without disclosed terms.
Deals that stood out
The quarter’s largest raise was an extension. EnerVenue raised a $300M Series B extension (we count that in the dollar total but not the milestone count) for nickel-hydrogen grid-scale energy storage, led by Full Vision Capital. Among milestone rounds, JetZero raised $175M, led by B Capital Group, for low-drag commercial airliners, and Heron Power raised $140M, co-led by Breakthrough Energy Ventures and a16z American Dynamism, for solid-state grid transformers.
Energy and the grid ran through the largest rounds. Beyond EnerVenue and Heron Power, Sage Geosystems raised $97M, co-led by Carbon Direct Capital Management and Ormat Technologies, for pressurized geothermal power and storage.
Cooling AI data centers showed up twice. Accelsius raised $65M, led by Johnson Controls, for two-phase liquid cooling, and Nautilus Data Technologies raised an undisclosed round, led by Pangaea Ventures, for liquid-cooling data-center infrastructure.
Only one Series B round was a biotech play: ecovia bio raised an undisclosed round for bio-based polyglutamic acid biopolymers, led by Pointe Angels.
The full Q1 2026 Series B list
All 14 U.S. climate tech Series B events from Q1 2026, ordered by round size. Company names link to the company, each amount links to the round’s source, and lead investors link to their sites.
- EnerVenue $300M*
- Nickel-hydrogen grid-scale energy storage
- Lead investors: Full Vision Capital
- Other investors: Hong Kong Investment Corporation Limited
- JetZero $175M
- Low-drag commercial airliners
- Lead investors: B Capital Group
- Other investors: United Airlines Ventures, Northrop Grumman Corporation, 3M Ventures, Trucks Venture Capital, Marlinspike, Aero X Ventures, RTX Ventures
- Heron Power $140M
- Solid-state transformers for the grid
- Lead investors: Breakthrough Energy Ventures, a16z American Dynamism
- Other investors: Capricorn Investment Group, Energy Impact Partners, Valor Atreides AI Fund, Gigascale Capital
- Sage Geosystems $97M
- Pressurized geothermal power and storage
- Lead investors: Carbon Direct Capital Management, Ormat Technologies
- Other investors: SiteGround Capital, The UC Berkeley Foundation’s Climate Solutions Fund, Exa Ventures, Nabors Industries, alfa8, Arch Meredith, Abilene Partners, Cubit Capital, Ignis H2 Energy
- Accelsius $65M
- Two-phase liquid cooling for data centers
- Lead investors: Johnson Controls
- Other investors: Legrand
- Hydrosat $60M
- Thermal satellite intelligence for agriculture
- Lead investors: Hartree Partners, Subutai Capital Partners, Space 4 Earth
- Other investors: Truffle Capital, Luxembourg Future Fund, OTB Ventures, Blue Bear Capital, Statkraft Ventures, Cultivation Capital, Santa Barbara Venture Partners
- Phoenix Tailings $30.2M*
- Clean rare-earth metals refining
- Lead investors: Olive Tree Capital
- Other investors: Traxys, Eni, Geodesic Alliance Fund, Aether VC, Envisioning Partners, MPower Partners
- Forerunner $26.3M
- Geospatial hazard-management platform for governments
- Lead investors: Wellington Management
- Other investors: SE Ventures, Citi Impact Fund, Gutter Capital, Bright Ventures, Union Square Ventures
- GlassPoint $20M
- Solar-thermal industrial process heat
- Lead investors: N.I.S. New Investment Solutions AG
- Other investors: MIG Capital AG
- AgZen $10M
- AI-guided sprayer coverage optimization
- Lead investors: DCVC Bio
- Other investors: Material Impact, Astanor Ventures, Syngenta Group Ventures
- Sepion Technologies $10M
- Nanoporous coated battery separators
- Lead investors: Fine Structure Ventures
- Other investors: W. L. Gore & Associates, Syensqo Ventures, VoLo Earth Ventures, Chailease, Catalus Capital, Impact Science Ventures, ACVC Partners
- Nautilus Data Technologies amount undisclosed
- Liquid-cooling infrastructure for data centers
- Lead investors: Pangaea Ventures
- Other investors: undisclosed
- ecovia bio amount undisclosed
- Bio-based polyglutamic acid biopolymers
- Lead investors: Pointe Angels
- Other investors: undisclosed
- Flair amount undisclosed
- Smart vents and HVAC zoning
- Lead investors: RectorSeal
- Other investors: Ulrich Gall, Skyview Ventures, Peter Nager, SOSV
- Interim rounds (e.g. an extension, second close, pre-Series A, etc). Our dollar totals include these; the round count does not.
Methodology
- Universe: U.S.-headquartered climate tech companies that announced a Series B round dated in Q1 2026 (January through March).
- Counting convention: dollar totals include extensions and second closes; round counts include milestone (primary) rounds only.
- Averages are computed within a single stage for rounds with disclosed amounts.
- Source: Planetary Scale climate funding database, built from public announcements and disclosures.
Planetary Scale is a fractional CFO and strategic finance firm for venture-backed climate tech startups. Learn more at www.planetaryscale.co