What are the top startups in the climate tech market?
In our climate tech market deck, you will find everything you need to understand the market
SUMMARY
Redwood Materials is the top climate tech startup today, followed by Form Energy and TerraPower, with Base Power and Antora Energy now firmly in the highest tier.
The ranking has shifted toward companies that can turn climate technology into infrastructure. Large factories, contracted capacity, repeat installations and construction progress now tell us more than another big funding round on its own.
Climate funding is growing again, but the rebound is narrow. More money is flowing into fewer companies, and the strongest pull is toward energy, storage, nuclear, industrial decarbonization and infrastructure that can serve AI-driven power demand.
Redwood stands out because much of the operating risk has already been removed. It handles large battery volumes, produces critical materials at industrial scale and is opening a second business by redeploying usable EV batteries into stationary storage before recycling them.
Form Energy shows the opposite tension: demand is running far ahead of deployment. An approximately 80 GWh backlog is extraordinary, but it also puts huge pressure on manufacturing to catch up with customers that have already committed at a scale the installed base has not yet proven.
Base Power is the fastest-moving newcomer. More than 500 MWh deployed in roughly three years suggests that climate products can scale much faster when customers are buying resilience and cheaper electricity rather than making an explicit climate purchase.
TerraPower has pushed advanced nuclear beyond the presentation-deck stage. Regulatory approval, construction, Meta-backed demand and an EPC framework for future reactors make it the strongest private nuclear company even though it has not produced a commercial kilowatt-hour yet.
Industrial heat storage has become a real deployment race. Antora has the most striking single scale jump with a 5 GWh project, while Rondo still has the stronger case on repeatability across different customers, countries and industrial processes.
Several companies now face a very different problem from the one they had a few years ago. Twelve, Stegra, Group14 and KoBold no longer mainly need to prove that the core idea works; they need to reproduce factories, plants or mines at commercial scale without letting costs and timelines break the model.
Fusion is also becoming less theoretical. Commonwealth Fusion Systems still has the stronger probability-adjusted case, but Helion has narrowed the gap by combining construction, licensing, measurable D-T fusion results and a commercial commitment from Microsoft.
The broader pattern is that climate tech is increasingly being bought for power, resilience, industrial productivity and strategic supply security as well as emissions reduction. That gives the strongest startups access to spending pools much larger than corporate sustainability budgets alone.
This market map, featured in our climate tech market deck, highlights top companies and startups in the climate tech market
Why is ranking the top climate tech startups harder now?
The top climate tech startups are harder to rank today because investors have become much more selective, while the strongest companies are moving from venture experiments into billion-dollar industrial projects.
Sightline Climate counted $40.5 billion of climate-tech venture and growth investment in 2025, up 8% from the previous year. At the same time, the number of deals fell 18% to 1,545. Put those two numbers together and the average amount of capital invested per deal increased by roughly 32%.
The concentration has continued. Currence measured $26.1 billion of climate-tech investment in the first half of 2026, up 55% year over year, while deal count fell another 25%. Ten deals absorbed 42% of all the money. Dealroom's latest climate dashboard reaches a lower $19.5 billion total because it uses a narrower definition, but it finds the same pattern: 61% of capital over the trailing four quarters went into rounds above $100 million.
That changes the question we need to answer. A startup with a clever carbon technology and a $50 million Series B now belongs to a very different universe from TerraPower building a commercial reactor, Antora commissioning a 5 GWh heat battery or Stegra trying to finish an entire steel plant. We have to judge whether these companies can turn technology into infrastructure.
What does “top climate tech startup” actually mean here?
For this ranking, a top climate tech startup is a private, independent company with unusually strong technology, commercial demand and evidence that it can actually deploy what it sells.
We give operating factories, contracted capacity, repeat installations and real customers considerably more weight than valuations. Funding still tells us something, particularly in businesses where building the first plant can cost hundreds of millions of dollars, but money raised is better treated as evidence that a company has resources to attempt the next step.
We also remove companies once they become public. Fervo Energy would otherwise rank near the top. Earlier this year, the geothermal company completed its Nasdaq IPO and raised about $2.2 billion including the underwriters' option. Its SEC filings showed 658 MW of binding power agreements representing roughly $7.2 billion of potential revenue backlog, plus a 3 GW development framework with Google. Fervo is an excellent benchmark for what a successful climate startup can become, but it has now graduated from this list.
The same applies to X-energy. The advanced nuclear company completed its own Nasdaq IPO earlier this year and is therefore outside our startup ranking, even though its roughly 11.5 GW identified project pipeline makes it an important comparison for TerraPower.
We are also keeping the climate-tech boundary reasonably tight. Companies benefiting from the AI power boom qualify when energy, storage, materials or decarbonization are actually central to the product. An AI data-center developer does not automatically become one of the world's top climate startups because a climate database happens to classify its low-carbon facilities as climate infrastructure.
As this chart shows, and as featured in our climate tech market deck, search interest in climate change has continued to rise
Is climate tech funding actually booming again?
Climate tech funding is growing again, but calling it a broad comeback would exaggerate what is happening.
Sightline found that energy attracted $14.4 billion in 2025, up 31% and the highest level in three years. Fusion and fission alone took 44% of that energy capital. Growth-stage investment jumped 78%, while seed funding fell 20% and Series A funding fell 7%.
The first half of 2026 made the concentration even more obvious. Currence's $26.1 billion total was 55% higher year over year, yet low-carbon data centers alone represented 34% of the money. DayOne's $4.5 billion round and Nscale's $2 billion financing accounted for roughly one-quarter of the entire dataset.
The more interesting change is happening underneath those headline numbers. AI companies need electricity quickly, utilities need storage, manufacturers want domestic supply chains, and governments care more about energy security. Climate technologies can increasingly sell reliability, speed, cheaper power or strategic independence alongside lower emissions.
That is one reason Form Energy can sell multi-day batteries to data-center developers, Redwood can turn used EV packs into grid storage, TerraPower can work with Meta, and Antora can sell thermal storage as an industrial energy product. These companies are benefiting from a much larger spending pool than corporate sustainability budgets alone.
| What the latest data shows | Scale | Our read |
|---|---|---|
| Sightline 2025 climate investment | $40.5B, +8% | Capital recovered |
| Sightline 2025 deal count | 1,545, -18% | Far fewer companies shared that capital |
| Implied average capital per deal | Roughly +32% | Funding became much more concentrated |
| Dealroom share going to $100M+ rounds | 61% | Scaleups dominate current financing |
| Currence H1 2026 investment | $26.1B, +55% | Headline growth looks very strong |
| Currence share from low-carbon data centers | 34% | AI power demand explains a large part of the jump |
Is Redwood Materials the strongest climate tech startup right now?
Redwood Materials is the strongest climate tech startup in our ranking today because it already operates at industrial scale while opening a second large business around energy storage.
Redwood currently receives more than 20 GWh of lithium-ion batteries each year and produces more than 60,000 metric tons of critical materials. The company says its processes recover more than 95% of lithium, nickel, cobalt and copper.
Those numbers are unusually large for a private climate company. Redwood says roughly 90% of lithium-ion batteries processed for recycling in North America pass through its facilities. Its Nevada campus now has more than two million square feet under roof, while its South Carolina operation has started recovering materials with an initial 20,000 metric tons of annual production capacity.
The business also became more interesting when Redwood stopped treating every used EV battery as recycling feedstock. Batteries that still have useful life can first become stationary storage. Redwood Energy launched around that idea and has already deployed second-life batteries with Crusoe for AI infrastructure.
Investors have followed that expansion. Redwood's latest Series E closed at $425 million after Google joined the round, and TechCrunch reported a post-money valuation above $6 billion.
What puts Redwood at number one for us is the amount of operational risk it has already removed. Collection works. Logistics work. Recycling works. Critical-material recovery works at meaningful volume. The newer question is how much value Redwood can add before those batteries finally reach the recycling line.
If you want more recent data on this point, please see our latest climate tech market report.
This chart, featured in our climate tech market deck, illustrates yearly VC funding for climate tech startups
Is Form Energy already the best long-duration battery startup?
Form Energy is the strongest long-duration battery startup today, although its commercial backlog is now running far ahead of the amount of hardware it has actually deployed.
Form's iron-air batteries can discharge for around 100 hours. That gives the company a different job from today's dominant lithium-ion grid batteries, which are usually designed around much shorter discharge periods.
Demand has accelerated dramatically. Form recently raised another $750 million, bringing total equity funding above $2 billion. TechCrunch reported an approximately 80 GWh commercial backlog, four times higher than earlier in the year.
The customers are also becoming more diverse. Crusoe reserved 12 GWh of Form batteries for AI data centers. Google and Xcel Energy are working on a Minnesota project involving 30 GWh of storage. FuturEnergy Ireland has a 1 GWh project. Form's first commercial Great River Energy installation, by comparison, is 150 MWh.
That creates one of the biggest gaps in this ranking. An 80 GWh backlog equals more than 500 times the energy capacity of Form's first commercial project.
That gap is both the reason Form ranks second and the reason it does not rank first. Customers have already made a huge bet on the product. Form now has to show that its West Virginia manufacturing system can reproduce iron-air batteries cheaply and reliably enough to satisfy demand that has grown much faster than its installed base.
How did Base Power become a top climate tech startup so quickly?
Base Power has become one of the top climate tech startups at extraordinary speed because it has already deployed more than 500 MWh of residential batteries while turning the home battery into part of the electricity system.
Base was founded only in 2023. It has since installed more than 500 MWh of storage, according to recent reporting from TechCrunch, and is currently installing roughly 100 batteries per day. Its latest financing added another $1 billion and valued the company at $13 billion post-money, less than a year after its previous $1 billion round.
The model explains why growth can be so fast. Base does not ask every homeowner to pay tens of thousands of dollars for a battery. Customers pay a much smaller installation fee, subscribe to the service and buy electricity from Base. The company then controls a distributed fleet of batteries that can charge when power is cheap and discharge when the grid needs it.
Its new Base Core system stores 39.2 kWh per battery, with customers able to install two units. That is unusually large for residential storage. The company has also moved beyond Texas into Illinois, putting its model inside PJM, the giant electricity market currently struggling with rapid data-center demand growth.
Base gives us one of the clearest examples of climate tech becoming attractive without requiring customers to make a climate decision. A homeowner can buy resilience and cheaper electricity. The same installation then becomes grid infrastructure.
The $13 billion valuation is aggressive for a company this young, and we would still rather own the operating proof than the valuation headline. More than 500 MWh deployed in roughly three years gives Base enough of that proof to rank near the top.
This chart, featured in our climate tech market deck, looks at First Solar’s strategy in climate tech
Is TerraPower ahead of every other advanced nuclear startup?
TerraPower is currently the strongest private advanced nuclear startup because it has moved further into actual commercial-plant construction than its private competitors.
The U.S. Nuclear Regulatory Commission approved the construction permit for TerraPower's first Natrium reactor in March 2026. Construction on the nuclear plant then formally began the following month. The NRC described the approval as the first construction permit for a commercial-scale advanced reactor.
Natrium combines a 345 MW sodium fast reactor with thermal storage that can increase output to around 500 MW when needed. TerraPower still needs an operating license before the plant can generate electricity, so several difficult years remain.
Commercial demand is already extending well beyond the Wyoming project. Meta has agreed with TerraPower to support development of up to eight Natrium plants, representing as much as 2.8 GW of baseload capacity and 4 GW when the storage systems are boosting output.
TerraPower has also added a fresh piece of the deployment puzzle. In its latest international update, the company said Hyundai Engineering & Construction had been selected under a framework covering up to eight future Natrium reactors, including completion, price and performance guarantees intended to make conventional project financing easier.
That is a big step. Advanced nuclear companies usually look convincing in reactor diagrams long before they look convincing as repeatable construction businesses. TerraPower is beginning to assemble the regulators, customers, EPC partners and financing structure that a fleet requires.
We still rank Redwood and Form higher because TerraPower has yet to produce a commercial kilowatt-hour. Among private advanced nuclear startups, though, TerraPower has moved into a position that is increasingly difficult for competitors to dismiss as theoretical.
If you want more recent data on this point, please see our latest climate tech market report.
Who is winning the industrial heat battery race, Antora or Rondo?
Antora Energy is now slightly ahead of Rondo Energy in our climate tech ranking because its 5 GWh Big Stone project has changed the scale of what a heat-battery startup has actually deployed.
Antora's system at POET's South Dakota bioprocessing plant contains more than 200 thermal batteries, stores 5 GWh and can deliver 50 MW around the clock. The project went from an empty site to delivering energy in less than a year. Full commissioning is still being completed, but the system is already supplying energy to the plant.
The jump in scale is enormous. Rondo's largest operating system stores 100 MWh, which means Big Stone has 50 times more energy capacity. Antora has since raised $550 million in Series C financing to increase manufacturing and deploy additional projects with industrial customers and hyperscalers.
Rondo still wins on repetition. Its 100 MWh California heat battery has been in commercial automatic operation, delivering continuous industrial steam from off-grid solar with reported round-trip efficiency above 97%. A separate 33 MWh system is operating at an SCG cement plant in Thailand and supplying 2.3 MW of continuous steam. Rondo says it now has 11 announced commercial developments, including eight heat-battery deployments, across five industries.
Rondo therefore gives us more evidence that the same basic product can work across customers and countries. Antora gives us much stronger evidence that thermal storage can suddenly become huge.
For now, we put Antora fifth overall and Rondo sixth. If Big Stone struggles during full commissioning, that order becomes debatable again. If Antora repeats a multi-gigawatt-hour project, the gap will widen quickly.
This chart, featured in our climate tech market deck, illustrates yearly funding for climate tech startups
Is Group14 actually producing silicon battery materials at EV scale?
Group14 has become one of the most commercially advanced battery-material startups because its silicon-anode technology is already coming out of a 10 GWh-scale factory rather than waiting for one to be built.
The company's SCC55 material replaces part or all of the graphite used in conventional lithium-ion battery anodes with silicon-rich material. The goal is straightforward: higher energy density and faster charging without redesigning the entire battery around a radically different chemistry.
Group14's South Korean BAM-3 factory is designed to produce 2,000 metric tons of SCC55 annually, enough for roughly 10 GWh of batteries. The facility began EV-scale production in 2026 after already shipping material to more than 100 battery and electronics customers.
The company also has evidence outside automotive development programs. Group14 says SCC55 is already inside millions of batteries manufactured by ATL for AI-enabled smartphones. That is useful because battery-material startups often spend years announcing qualification agreements without reaching mass-produced products.
Group14 raised $463 million in its Series D and took full control of the South Korean factory from its former joint venture with SK. Total equity raised has passed $1 billion.
We rank Group14 below the largest energy-infrastructure companies because being qualified in a battery is only one part of building a dominant material supplier. Still, a 10 GWh commercial factory and more than 100 customers put Group14 well beyond the stage where silicon anodes are mainly a laboratory promise.
Has Twelve actually made e-fuels commercially real?
Twelve has made power-to-liquid jet fuel commercially real in the United States, but its first plant also shows just how far e-fuels still have to scale.
AirPlant One in Washington began commercial operations in June 2026. The facility produces E-Jet sustainable aviation fuel and E-Naphtha from carbon dioxide, water and renewable electricity. Twelve says it is already producing on-spec fuel that is being delivered and sold for commercial aviation use.
That is an important distinction in sustainable aviation. Plenty of companies have announced future e-fuel plants. Twelve now has an operating facility making a certified drop-in fuel.
The numbers get more sobering when we compare AirPlant One with Twelve's sales ambitions. The plant was designed for an initial E-Jet capacity of roughly 40,000 gallons per year. International Airlines Group has a 14-year agreement for 260 million gallons of Twelve fuel.
Spread evenly across 14 years, the IAG agreement represents about 18.6 million gallons annually. That is roughly 465 times AirPlant One's initial yearly output.
Twelve obviously does not plan to fulfill the contract from one plant. The comparison tells us what the next phase really involves: reproducing AirPlant One hundreds of times in capacity terms.
Its financing is structured with that problem in mind. Twelve previously announced $645 million of funding that included up to $400 million of project equity from TPG Rise Climate for future AirPlants. That shift toward project capital is exactly what we want to see from a company whose biggest challenge has moved from chemistry to construction.
If you want more recent data on this point, please see our latest climate tech market report.
This chart, featured in our climate tech market deck, compares the main business model options for carbon management platforms
Can Stegra still be a top climate startup after needing another €1.4 billion?
Stegra still belongs among the top climate tech startups, but the company's latest €1.4 billion financing makes its execution risk impossible to treat as a footnote.
The Boden project in northern Sweden is trying to integrate renewable electricity, a 700 MW electrolyzer, hydrogen production, direct-reduced iron and steelmaking on one site. Stegra says the process can cut emissions from ore-based steel by as much as 95%.
Physical construction is far advanced. All 37 electrolyzer modules are installed, the direct-reduction tower has risen above 100 meters, and equipment installation is progressing throughout the steel mill. Stegra aims to supply five million tonnes of green steel annually by 2030.
Demand has existed for years. The company had already pre-sold more than 1.5 million tonnes of green steel by 2022, and customers have included Mercedes-Benz, BMW, Porsche, Scania, Schaeffler, Microsoft and thyssenkrupp Materials Services.
Yet customer demand did not remove the financial strain of building one of Europe's largest new industrial complexes. Stegra closed another €1.4 billion financing round in June 2026. The money covers higher project costs, added infrastructure scope and a larger financial buffer. During fundraising, construction slowed, and the company said its project timeline was under review.
That is why Stegra sits below the modular storage and battery-material companies in our ranking. A successful Boden plant could remove millions of tonnes of annual emissions and create a new industrial model for steel. A major delay or another cost overrun would also hit Stegra far harder than a company that can build its product one module at a time.
Who is actually ahead in fusion, Commonwealth Fusion Systems or Helion?
Commonwealth Fusion Systems is still our stronger fusion startup overall, while Helion has recently closed much more of the gap than the valuation alone suggests.
CFS recently raised another $1 billion, taking total capital raised to $4 billion. The company says that represents roughly 30% of all private fusion capital raised globally. Its SPARC demonstration machine is approaching final assembly, while development of the ARC commercial power station in Virginia is happening in parallel.
CFS also has real prospective buyers for ARC. Google has agreed to purchase 200 MW, while Eni has signed a power agreement worth more than $1 billion. CFS says Google and Eni together have contracted for more than half of the plant's expected electricity.
Helion is pursuing a more aggressive timeline. Its latest $465 million round valued the company at $15.5 billion and brought total investment to $1.5 billion. Polaris has demonstrated measurable deuterium-tritium fusion and plasma temperatures above 150 million degrees Celsius.
Helion has also moved rapidly on construction and regulation. Orion, its first commercial plant, is under construction in Washington. The company has obtained radioactive-material and air-emissions licenses from the state, while work has started on the generator building. Microsoft has contracted for at least 50 MW, with initial operations still targeted for 2028.
The comparison comes down to the type of risk we are willing to accept. CFS gives us a more conventional tokamak architecture, a large scientific foundation, extensive external publication and an early-2030s commercialization target. Helion gives us a more unusual machine, direct electricity conversion and a timeline that would put commercial fusion on the grid several years earlier.
We rank CFS ahead because the probability-adjusted case still looks stronger. Helion now deserves a much narrower discount than it did a year ago because Orion construction, Polaris results and regulatory approvals have converted several promises into observable milestones.
If you want more recent data on this point, please see our latest climate tech market report.
| Current comparison | Commonwealth Fusion Systems | Helion |
|---|---|---|
| Capital raised | About $4B | About $1.5B |
| Commercial plant | ARC, Virginia | Orion, Washington |
| Customer proof | Google 200 MW; Eni agreement >$1B | Microsoft ≥50 MW |
| Latest technical stage | SPARC approaching final assembly | Polaris demonstrated D-T fusion above 150M°C |
| Commercial target | Early 2030s | Initial Orion operations targeted for 2028 |
| Our ranking | Higher probability of eventual commercialization | Faster path if its technical assumptions hold |
This chart, featured in our climate tech market deck, breaks down market revenue by customer segment in the climate tech market
Does KoBold Metals really belong among the top climate tech startups?
KoBold Metals deserves a place near the bottom of our top 12 because its AI-driven exploration model has produced a mine project large enough to affect the global copper market.
KoBold uses data science and machine learning to improve mineral exploration, focusing on metals such as copper, lithium, nickel and cobalt. The climate connection comes through the enormous material requirements of grids, electric vehicles, batteries and electrification.
The important evidence is Mingomba in Zambia. KoBold and state-backed ZCCM-IH have formally started work on the project, with expected investment above $2 billion. The mine is targeting around 300,000 metric tons of copper production per year once operating in the early 2030s.
At that scale, Mingomba would be a major copper mine rather than a technology demonstration. KoBold has therefore shown that its exploration approach can identify an asset important enough to justify multibillion-dollar development.
The caveat is obvious. KoBold does not yet produce those 300,000 tonnes. Building a mine is slow, politically complicated and capital intensive, and mining itself has substantial environmental costs.
We still include KoBold because climate infrastructure ultimately runs into physical material constraints. Finding another major source of copper can matter as much to electrification as improving the efficiency of one individual device.
Why don't Climeworks, Charm and Watershed make our top 12?
Climeworks, Charm Industrial and Watershed remain important climate companies, but current operating scale puts them just outside our top 12.
Climeworks is still the defining direct-air-capture company. It has raised more than $1 billion of equity, while its Mammoth facility in Iceland has a nameplate capacity of up to 36,000 tonnes of CO2 removal per year. That combination also exposes the problem. The company has attracted extraordinary capital, yet the physical amount of carbon removed remains small relative to the emissions problem it is trying to solve.
Charm gives us a more encouraging commercial structure. JPMorganChase recently expanded its purchase commitment by 61,500 tonnes, bringing its total commitment with Charm to 90,000 tonnes, and separately provided a $20 million debt facility to expand Charm's Colorado operations. The interesting part here is the move from venture financing toward a customer helping finance future supply.
Watershed has a different kind of scale. The company says more than $500 million of new clean-energy investment has now been driven through its customers, financing more than 270 solar and wind projects across six countries and almost 400 MW of new capacity. That makes Watershed much more than a carbon-accounting dashboard.
All three could move higher. For carbon removal, we want much larger volumes of delivered tonnes. For Watershed, we want continued proof that its procurement layer creates enough economic value to remain differentiated as carbon accounting becomes easier to replicate.
Boston Metal and Electra are in a similar waiting room. Both are attacking industrial metals with serious technology and commercial partners, but their biggest projects still need to cross into sustained large-scale production.
This chart, featured in our climate tech market deck, shows how personal carbon tracking app technology has evolved over time
So which climate tech startups are actually on top today?
Redwood Materials is our number-one climate tech startup today, followed by Form Energy and TerraPower, while Base Power and Antora have moved sharply upward because recent deployment evidence is stronger than it was even a few months ago.
The biggest change from a simple funding-based ranking is how many famous climate companies fall down the list. We give Redwood's 60,000 tonnes of annual material production more credit than a speculative valuation. We give Antora's 5 GWh project more credit than a pilot announcement. We give Twelve's operating fuel plant more credit than a future SAF reservation on its own.
Base Power is the clearest new entrant into the highest tier. More than 500 MWh deployed, roughly 100 battery installations a day and a move into a second major electricity market give us unusually strong operating evidence for a company founded only three years ago.
Group14 also moves into our top 12 because a 10 GWh-scale silicon-material factory is stronger proof than another battery-material qualification announcement. Conversely, carbon removal loses places because even its strongest companies remain small when measured by tonnes physically removed.
The resulting list is heavily tilted toward energy, storage and industrial infrastructure. That reflects where climate tech is today. Power demand is rising, AI infrastructure is creating urgent new buyers, supply-chain security has become politically important, and late-stage capital is concentrating around companies that can build physical assets.
If you want more recent data on this point, please see our latest climate tech market report.
| Rank | Climate tech startup | Why we rank it here | Biggest thing still unproven |
|---|---|---|---|
| 1 | Redwood Materials | >60,000 tonnes of annual critical-material production, >20 GWh of batteries received annually and a new second-life storage business | How large the integrated storage and battery-material platform can become |
| 2 | Form Energy | 100-hour iron-air storage with roughly 80 GWh of commercial backlog | Whether manufacturing can scale fast enough to match that backlog |
| 3 | TerraPower | First commercial-scale advanced-reactor construction permit, plant under construction and Meta backing for up to eight units | Completing and operating the first Natrium reactor |
| 4 | Base Power | >500 MWh of distributed batteries deployed and roughly 100 installations per day | Whether the economics remain attractive as it expands far beyond Texas |
| 5 | Antora Energy | 5 GWh Big Stone heat battery already delivering energy and a fresh $550M financing | Repeating multi-GWh deployments with new customers |
| 6 | Rondo Energy | Multiple operating industrial heat batteries across the U.S. and Asia, plus deployments with major industrial customers | Moving from hundreds of MWh to repeated GWh-scale projects |
| 7 | Group14 Technologies | Silicon-anode material in mass-produced batteries and a 10 GWh-scale factory ramping production | Winning enough EV programs to fill large-scale capacity |
| 8 | Twelve | Commercial E-Jet production is now operating and fuel is being sold | Expanding output by hundreds of times while keeping economics viable |
| 9 | Stegra | One of the world's largest green-steel projects, 700 MW of electrolysis and major contracted customers | Completing Boden after higher costs and schedule pressure |
| 10 | Commonwealth Fusion Systems | $4B raised, SPARC nearing completion and commercial power commitments from Google and Eni | Demonstrating net-energy fusion and then building ARC |
| 11 | Helion | Orion under construction, key regulatory licenses secured and Microsoft contracted for ≥50 MW | Producing commercial fusion electricity on its unusually fast timeline |
| 12 | KoBold Metals | Mingomba has moved from AI-assisted exploration into a >$2B mine targeting 300,000 tonnes of copper annually | Building the mine and proving that the exploration model can repeatedly find assets this large |
OUR METHODOLOGY
There is no single metric that tells us which climate tech startups are genuinely ahead, so we broke the question into six analytical dimensions: operational scale, commercial validation, repeatability, remaining execution risk, progress along the relevant commercialization path, and the strength of the overall evidence.
For each dimension, we looked for the freshest available evidence and assessed it together rather than letting one headline number determine the result. Funding matters more when it accompanies manufacturing expansion. A customer agreement carries more weight once deployment has started. A technically ambitious project becomes much more credible once regulatory, construction or operating milestones are visible.
We also adapted the evidence to the company. Battery and materials companies can be judged through deployed capacity, factory output and repeat installations; advanced nuclear and fusion companies cannot yet be measured the same way, so we looked instead at regulatory approvals, construction progress, technical validation and binding commercial demand. The point was to measure how far each company has moved along the commercialization path that actually matters for its business.
We kept scale and repeatability separate. A huge first project can materially de-risk a technology, while several operating projects show that the company can reproduce it across customers and locations. That distinction is especially important in comparisons such as Antora versus Rondo, or Form Energy's backlog versus its installed base.
The final ranking is an aggregation of evidence rather than a score built around arbitrary numerical weights. We looked for cases where several pieces lined up at once: technology moving into operation, customers committing real demand, deployment becoming repeatable, financing supporting the next stage, and the remaining execution gap getting narrower.
Key sources used in the analysis include Dealroom's climate dashboard, Redwood Materials' operating and recovery data, Form Energy's deployment and storage data, Form Energy's Crusoe agreement, the U.S. Nuclear Regulatory Commission's TerraPower construction-permit record, TerraPower's Meta agreement, Rondo Energy's Thailand deployment, Twelve's AirPlant One operating update, Stegra's 2026 financing update, Commonwealth Fusion Systems' latest financing disclosure, Helion's Polaris technical update, and KoBold Metals' Mingomba construction update.
In our climate tech market deck, we identify pain points entrepreneurs should prioritize
