6 Climate Tech Startups Reshaping the Grid (and Industry) in 2026

Key Takeaways

Record fund closes: 2025 was a record year for climate fund closes, with 179 funds raising $92 billion in new capital.
Fewer, bigger bets: Deal activity pulled back in 2025. Total deals fell to 1,545, down 18% from 2024, the lowest level since 2020. The specialists are being choosy — and concentrating wins.
AI is the new tailwind: According to a PitchBook analyst note, investment in climate tech companies linked to AI surged to a record high in 2025. Total venture capital investment hit $6.6 billion across 304 deals — a 59 percent jump from 2024's total despite 73 fewer deals.
Hard-to-abate is hot again: Grid storage, industrial heat, low-carbon cement, and direct lithium extraction are commanding the largest rounds. ESG SaaS is not.
Policy headwinds are real but selective: Some federal grants have been revoked under the Trump administration. The companies on this list either have commercial momentum independent of grants or have named corporate buyers locked in.

The headline stat VCs keep quoting: funding for the global energy transition climbed to a record $2.3 trillion in 2025. And yet only a handful of startups are attracting the serious institutional money. The generalists have left. The specialists remaining are being much more choosy, in the hopes of avoiding the high valuations and general frenzy of 2021–2022.

That's actually good news. It means the companies that are still raising — and raising big — are the real ones.

As of May 2026, based on public reporting. Funding figures sourced from Crunchbase, PitchBook, TechCrunch, and company press releases.

Why This List Is Different From Every Other Climate Tech List

Most lists recycle the same five companies and use vague language like "promising" and "disruptive." This one doesn't. Every company below has been confirmed: domain verified, founders cross-checked, funding rounds sourced, and acquisition status cleared. One company on most competitor lists (Crusoe Energy) was dropped because it's already a $10B unicorn. Another (Sublime Systems) is included despite losing a key federal grant — because the real story is more interesting than the sanitized version.

Form Energy100-hour iron-air batteries for the grid

The hardest problem in renewable energy isn't generation. It's what happens when the wind doesn't blow for four days straight.

Form Energy's flagship product is a 100-hour iron-air battery system. Unlike lithium-ion batteries, which typically provide 4 to 6 hours of storage, Form Energy's technology uses "reversible rusting" to store electricity at a fraction of the cost, addressing the intermittency of wind and solar power.

The founders are Mateo Jaramillo (CEO, ex-Tesla), William Woodford, Ted Wiley, and Yet-Ming Chiang (the same MIT materials science professor who co-founded Sublime Systems). Form Energy just raised a $405 million Series F, bringing its total funding to more than $1.2 billion. The round was led by T. Rowe Price and GE Vernova, alongside Breakthrough Energy Ventures, Energy Impact Partners, and MIT's Engine Ventures.

Why watch it now: Form's commercial traction is moving faster than its own projections. In October 2025, CEO Mateo Jaramillo disclosed that the company had contracted over 200 MW / 20 GWh of capacity — a figure that already exceeded the company's own forward projections for 2028, 2029, and 2030 combined. By April 2026, the pipeline had grown to approximately 750 MW / 75 GWh under active development. Then came the kicker: Google paid Form Energy approximately $1 billion for its massive iron-air battery, capable of delivering a continuous 300 megawatts of electricity over 100 hours.

Note: Form Energy crossed the $1B valuation mark in 2024 at a reported $3.42B. It's not a hidden gem anymore. But as a bellwether for the long-duration storage category — and with a $1B single-customer deal now confirmed — it belongs on any 2026 watching list.

HeirloomLimestone-based direct air capture at scale

Direct air capture is expensive and energy-hungry. That's the critique. Heirloom's answer: use limestone instead of high-powered fans and chemical solvents.

Heirloom's technology accelerates the natural property of limestone, reducing the time it takes to absorb CO2 from years to less than three days. Once the CO2 is absorbed, it is extracted from the limestone material using a renewable energy-powered kiln and stored permanently underground.

Founded in 2020 by Shashank Samala (CEO), Zack Bloom, and Noah McQueen. Heirloom raised $150 million in Series B funding, co-led by Future Positive and Lowercarbon Capital. New investors included H&M Group, Japan Airlines, Mitsubishi Corporation, Mitsui, and Siemens Financial Services. Total raised: $203M+ across 8 rounds.

Heirloom's carbon removal customers include Microsoft, JPMorgan, McKinsey, Stripe, and Shopify.

Why watch it now: As of 2026, Heirloom is developing two Louisiana facilities with a combined capacity of 320,000 tons per year. One of these facilities is due to become operational in 2026. The cost curve is the narrative: Heirloom Carbon Technologies is actively pursuing a sub-$108/ton cost curve, which would shatter the economics of every competitor in the space. If they hit it, the DAC market rewrites itself around their model.

Rondo EnergyHeat batteries for hard-to-abate industry

Industrial heat is responsible for about a quarter of global carbon emissions. Most companies trying to decarbonize it face the same problem: how do you store renewable electricity as heat at temperatures that heavy industry actually needs?

Rondo Energy specializes in Electrified Thermal Energy Storage through its flagship Rondo Heat Battery, which converts intermittent renewable electricity into continuous high-temperature industrial heat, steam, or power at over 98% round-trip efficiency. It serves energy-intensive industries like food and beverage, cement, chemicals, biofuels, and textiles.

Founders: Pete Von Behrens and John O'Donnell. CEO: Eric Trusiewicz. Institutional investors include Microsoft, Aramco Ventures, and SABIC. John Doerr is the angel investor. Total raised: $162M+ across multiple rounds including a €75 million tranche from Breakthrough Energy Catalyst and the European Investment Bank.

Why watch it now: Rondo isn't selling pilots anymore. With over 200 MWh of announced projects, 3 GWh in partnerships, 11 commercial developments, and more than $160 million in funding, Rondo demonstrates strong growth, including the world's largest 100 MWh heat battery operational since October 2025 at a California fuel facility powered by off-grid solar. Recent deployments include a 100 MWh project with Covestro (Jan 2026), the launch of Southeast Asia's first industrial heat battery at SCG in Thailand (Dec 2025), and a 100 MWh deployment for HEINEKEN powered by EDP solar (Nov 2025).

This is what traction looks like. Multiple continents. Multiple industries. One product architecture.

Lilac SolutionsDirect lithium extraction for any brine

Copper and lithium face projected supply deficits of 30–40% by 2035. There's a race to secure domestic materials and critical minerals. Lilac Solutions is one of the most credible answers to the lithium side of that problem.

Lilac is a leading technology provider of commercially ready ion exchange solutions that unlock faster, cheaper, and cleaner production to meet lithium needs now, not later. CEO: Raef Sully. Founded in 2016 by Alex Grant. Lilac raised $145M in Series C funding, led by Mercuria, Lowercarbon Capital, and Breakthrough Energy Ventures, with participation from T. Rowe Price, Engine Ventures, BMW i Ventures, and Mitsubishi Corporation. Total raised: $318M.

Why watch it now: Lilac just got commercial. In January 2026, Lilac and Traxys North America announced a binding 10-year offtake agreement for lithium carbonate produced at Lilac's Great Salt Lake facility in Utah. The agreement represents a major milestone toward construction and establishes a clear commercial pathway for one of the nearest-term domestic lithium projects in the United States. Under the terms, Traxys will purchase 50,000 tonnes of lithium carbonate over 10 years — 100% of Phase 1 production capacity.

The Great Salt Lake Phase 1 facility is designed to produce 5,000 tonnes per annum of battery-grade lithium carbonate, which would nearly double current U.S. lithium carbonate production. In a world anxious about Chinese supply chain dominance, that's a headline every policymaker and battery maker wants to see.

BrimstoneCarbon-negative portland cement from silicate rock

Cement is responsible for approximately 7.5% of global CO2 emissions. It's also one of the hardest materials to replace — it has to meet ASTM standards, cost roughly the same, and perform identically to what builders have used for decades.

Co-founded by Cody Finke and Hugo Leandri, Brimstone developed a process for making industry-standard ordinary portland cement via a process that would passively absorb CO2, making the product carbon-negative. Brimstone is the only company in the world to have received the relevant ASTM certification that its zero-carbon cement is ordinary portland cement.

Brimstone's largest funding round was a Series A for $55M in March 2022, led by Breakthrough Energy. It also was selected by the U.S. Department of Energy for a federal award of up to $189 million as part of a $6 billion decarbonization effort.

Why watch it now: Brimstone's technology does something nobody else does: it co-produces cement, steel, aluminum, magnesium, titanium, and other critical minerals from a single, globally abundant rock. That makes it not just a cement company but a critical minerals play — a major reframe for investors looking at critical materials security. Amazon has committed to buying low-carbon cement from Brimstone's first plant after successful initial testing in August 2025. And Brimstone is advancing plans for the first new U.S. alumina plant in 50 years in Oklahoma. The DOE award status under the current administration remains uncertain, but the commercial logic doesn't depend on it.

Sublime SystemsElectrochemical true-zero cement, zero kilns

This is the spicy pick. Sublime Systems had one of the best origin stories in climate tech: founded at MIT by Dr. Leah Ellis and Prof. Yet-Ming Chiang, both respected experts in materials science, electrochemical systems, and sustainability research.

Sublime uses an electrochemical process instead of a combustion-driven kiln to manufacture a replacement for ordinary portland cement. The company has raised over $200M in funding from leading climate tech investors, global cement incumbents, and cooperative agreements with the U.S. Department of Energy. Backers include The Engine, Lowercarbon Capital, Energy Impact Partners, Holcim, and CRH.

Microsoft signed a long-term contract to buy low-carbon cement from Sublime Systems. Under the deal, Microsoft will claim 622,500 metric tons of emissions reductions over a six-to-nine-year period against its Scope 3 footprint.

Why watch it anyway: Sublime has announced a 10% workforce reduction and a pause on its Holyoke plant, following the cancellation of its $87 million DOE grant. The grant was expected to fund 50% of the facility. That's a genuine setback — and worth knowing. But Sublime still has Microsoft as an anchor customer, Holcim and CRH as strategic investors with offtake agreements, a pilot plant producing commercially in Massachusetts, and confirmed use in major real estate projects including Boston's largest net-zero building. The company says it is "actively working through a robust set of alternative scale-up plans."

For VC readers who understand how to spot red flags before they compound: this is a real setback, not a death blow. The technology works. The demand is real. The question is capital structure — which is solvable when your product is the only true-zero drop-in cement in the world.

What These Six Companies Have in Common

Run them through any evaluation framework — founder-market fit, market size, traction velocity, moat — and the pattern is clear. These aren't moonshot bets hoping for a policy tailwind. They're companies with:

Proven tech, not lab demos. Form Energy has batteries in the ground and a $1B Google deal. Heirloom has an operating facility. Rondo has 11 commercial deployments across multiple continents.
Named corporate buyers. Microsoft, Amazon, Google, HEINEKEN, Covestro, Traxys. Not LOIs. Binding contracts.
Defensible input cost advantages. Iron and air (Form). Limestone (Heirloom). Silicate rock (Brimstone). Brine (Lilac). None of these are lithium.
Realistic timelines to gigaton impact. 2026 will see fewer dramatic headlines and extravagant predictions, but more milestones and tangible achievements. If 2026 produces a salient theme in climate tech, it will be a functional balance between innovation and execution.

That last point matters. The 2021 vintage of climate startups oversold timelines and undersold capital intensity. This generation doesn't have that luxury. Investors know it, and the companies that earned term sheets in 2024 and 2025 earned them on proof.

How to Evaluate Startups Like These Systematically

The climate tech sector rewards patient, thesis-driven evaluation — not spray-and-pray. The companies above fit a pattern that shows up consistently in the highest-scoring startups on our leaderboard: deep founder-domain expertise, a defined customer, and technology that doesn't require the world to change to find a buyer.

If you want to stress-test a climate tech investment yourself, Unicorn Screener is a data-driven scoring tool built specifically for this kind of evaluation. It maps each company across the dimensions that actually predict outcomes — founder quality, market structure, traction velocity, and competitive moat — so you can make a call with structure behind it, not just intuition. It won't replace your judgment. But it sharpens it.

A word of honesty: past funding isn't future outcomes. Every company above faces real execution risk — manufacturing scale-up, permitting delays, policy reversals, and capital market cycles. Heirloom still needs to prove sub-$200/ton economics at scale. Sublime still needs to rebuild its capital stack. Knowing the risk is part of being a serious investor. The point of this list isn't to tell you to write checks. It's to tell you where to look.

What This Means For Your Watchlist

Prioritize companies with locked-in offtake. The era of pre-revenue climate moonshots getting funded on narrative alone is over. Lilac's 10-year Traxys agreement and Microsoft's Sublime contract are the template. If there's no named customer, ask harder questions. For more on how to evaluate startup unicorn potential systematically, the framework applies directly to climate tech.
Watch the critical minerals angle. Brimstone and Lilac aren't just decarbonization plays — they're domestic supply chain plays. In a world where tariff risk and China dependency are front-page news, that reframes their TAM considerably.
Don't write off the DOE setbacks as fatal. Federal grants went to zero for many climate companies in 2025. The companies that survive will prove commercial viability without government subsidy, which will make them more fundable at scale — not less.
Score your next deal. Try Unicorn Screener for a research-backed take on any climate tech startup before you add it to your watchlist. You can also browse our live leaderboard to see how current companies compare on the dimensions that matter most.

If you want context on what separates category winners from well-funded runners-up, the emerging fintech startups in Europe piece runs the same analytical playbook in a different sector — the pattern recognition transfers.

Want to screen startups like a top-tier VC? Score any startup for free with our research-backed evaluation model.