As the world accelerates toward a carbon-neutral future, cleantech startups are emerging as critical drivers of innovation in the fight against climate change. In 2026, the cleantech sector has reached a pivotal moment where breakthrough technologies are transitioning from laboratory concepts to commercial deployment. With global investment in cleantech exceeding the trillion-dollar mark and increasing pressure from regulatory frameworks, consumers, and investors alike, these startups are reshaping how we generate, store, and manage energy. This comprehensive guide explores the ten most promising cleantech startups that are not only attracting significant capital but also demonstrating real-world viability and scalability.
1. Oklo Inc.: Revolutionizing Nuclear Energy with Advanced Fission
Leading the cleantech revolution is Oklo Inc., a California-based company that is redefining nuclear power through advanced fission technology. Founded in 2013 and now publicly traded on the NYSE under the ticker OKLO, the company has made remarkable progress in developing small modular reactors that address the longstanding challenges of traditional nuclear power.
Oklo’s flagship product, the Aurora powerhouse, represents a paradigm shift in nuclear technology. These compact reactors can generate between 15 and 75 megawatts of electrical power and are designed to operate for up to ten years without refueling. What sets Oklo apart is its use of liquid-metal-cooled, metal-fueled fast reactors with over 400 reactor-years of demonstrated operating experience worldwide. The company has achieved several historic milestones, including becoming the first to receive a site use permit from the U.S. Department of Energy for a commercial advanced fission plant and submitting the first custom combined license application for an advanced reactor to the Nuclear Regulatory Commission.
In January 2026, Oklo announced a groundbreaking agreement with Meta Platforms to develop a 1.2-gigawatt power campus in Pike County, Ohio. This partnership represents one of the most significant commitments to advanced nuclear energy by a technology company and highlights the growing demand for clean, reliable baseload power to support AI data centers and other energy-intensive operations. Meta’s agreement includes prepayment for power and funding to advance project certainty, with pre-construction activities beginning in 2026 and the first phase targeted to come online by 2030. The deal sent Oklo’s stock surging over 20 percent in early January, reflecting investor confidence in the company’s technology and business model.
Oklo’s approach extends beyond electricity generation. The company is also developing nuclear fuel recycling technologies that can convert used nuclear fuel into clean energy, effectively addressing one of nuclear power’s most persistent challenges. Additionally, through a partnership with the Department of Energy’s Reactor Pilot Program, Oklo is establishing a domestic supply chain for critical radioisotopes used in cancer treatment and medical applications. This diversified approach positions Oklo not just as an energy company but as a comprehensive nuclear technology provider addressing multiple market needs.
2. Watershed: Leading the Carbon Management Revolution
In an era where carbon accounting has become as essential as financial accounting, Watershed stands out as the premier enterprise sustainability platform. Founded in 2019 by former Stripe employees Taylor Francis, Avi Itskovich, and Christian Anderson, this San Francisco-based company has rapidly become the gold standard for organizations serious about their climate commitments. With a valuation of $1.8 billion following a $100 million Series C funding round in early 2024, Watershed has positioned itself at the intersection of climate action and enterprise software.
Watershed’s platform addresses one of the most complex challenges facing modern corporations: measuring, reporting, and reducing carbon emissions across all three scopes, including the notoriously difficult Scope 3 emissions that encompass the entire value chain. The company serves hundreds of high-profile clients including Walmart, FedEx, General Mills, BlackRock, Stripe, and Bain Capital. What distinguishes Watershed from its competitors is its comprehensive approach that goes beyond mere measurement to provide actionable reduction strategies, supplier engagement tools, and connections to high-quality carbon removal projects.
The platform features over 60 pre-built integrations with existing business systems, allowing companies to ingest carbon data directly from their enterprise resource planning systems, travel booking tools, and other operational software. Watershed’s proprietary carbon data engine automatically detects anomalies and assigns granular, science-based emissions factors based on tens of thousands of benchmarks and emissions models. The company has achieved a remarkable milestone: 100 percent of Watershed customer footprints have passed audits, demonstrating the platform’s reliability and adherence to the highest accounting standards.
As regulatory pressure intensifies globally, with climate disclosure now required for large companies in the UK and Europe, Watershed is positioned at the forefront of the carbon management software market, which is projected to reach $1.2 billion by 2028. The company’s mission to help reduce half a gigaton of greenhouse gas emissions by 2030 reflects its ambitious vision for corporate climate action. In 2026, Watershed continues to expand its capabilities, particularly in supplier engagement and product carbon footprint analysis, making it an indispensable tool for companies navigating the transition to a low-carbon economy.
3. Helion Energy: Pursuing the Holy Grail of Fusion Power
Helion Energy represents one of the most ambitious endeavors in cleantech: commercializing fusion energy, the same process that powers the sun. Based in Everett, Washington, and backed by prominent investors including OpenAI CEO Sam Altman, Facebook co-founder Dustin Moskovitz, and steel manufacturer Nucor, Helion has raised $425 million in its most recent funding round, pushing its valuation to $5.245 billion. The company made headlines in 2023 by securing the world’s first commercial fusion power purchase agreement with Microsoft, committing to deliver 50 megawatts of electricity by 2028.
Helion’s approach to fusion differs fundamentally from traditional tokamak designs. The company has developed a pulsed magneto-inertial fusion system based on field-reversed configuration plasma technology. This innovative approach uses powerful magnets to create rings of ultra-hot plasma that are propelled at each other at speeds exceeding one million miles per hour, generating temperatures above 100 million degrees Celsius and triggering fusion reactions. Critically, Helion’s system directly converts fusion energy into electricity without the need for steam turbines or other intermediate conversion steps, potentially achieving round-trip efficiency of over 95 percent.
The company broke ground on its Orion plant in Malaga, Washington, in 2025, marking a significant transition from research to commercial deployment. To support this ambitious timeline, Helion has established a 166,000-square-foot manufacturing facility near its Everett headquarters where it will produce the approximately 2,500 capacitor units needed for the Orion plant. Production is scheduled to begin in late 2026, with the facility eventually producing components for multiple fusion plants.
While Helion’s timeline has drawn skepticism from some nuclear experts, particularly regarding whether the company has achieved net energy gain, its progress cannot be dismissed. The company has successfully demonstrated plasma formation, magnetic energy recovery at scale, and fusion reactions producing neutrons. In 2026, Helion is focused on scaling its manufacturing capabilities and advancing its Polaris prototype system. If successful, Helion’s technology could provide virtually limitless clean energy, fundamentally transforming the global energy landscape and cementing its position as one of the most consequential cleantech companies of the decade.
4. Form Energy: Revolutionizing Grid Storage with Iron-Air Batteries
Form Energy is tackling one of renewable energy’s most critical challenges: long-duration energy storage. Founded by five co-founders including MIT Professor Yet-Ming Chiang and former Tesla Powerwall developer Mateo Jaramillo, this Massachusetts-based company has developed an iron-air battery system capable of storing electricity for up to 100 hours at system costs competitive with legacy power plants. This breakthrough technology addresses a fundamental limitation of lithium-ion batteries, which typically provide only a few hours of storage due to their high costs.
The innovation at the heart of Form Energy’s technology is elegantly simple: reversible rusting. When discharging, metallic iron inside the battery reacts with oxygen from the air and water from the electrolyte to form iron hydroxide, essentially rust, releasing electrons and generating electricity. When charging, excess electricity from the grid reverses the reaction, separating oxygen and water from the iron and returning it to its metallic state. This process can be repeated thousands of times, delivering electricity when and where it is needed most. Made from iron, water, and air—some of the most abundant and inexpensive materials on Earth—Form’s batteries can be produced at approximately one-tenth the cost of lithium-ion systems.
Form Energy has successfully raised over $800 million and completed construction of its 550,000-square-foot manufacturing facility, Form Factory 1, in Weirton, West Virginia, on the historic site of the former Weirton Steel mill. The facility employs over 300 people and has begun producing battery systems for multiple utility partners. The company’s first commercial pilot, a 1.5-megawatt, 150-megawatt-hour project with Great River Energy in Minnesota, began operation in 2025. Additional projects are underway across the United States, including a 5-megawatt system in California backed by a $30 million grant from the California Energy Commission, expected to go live in early 2026, and multiple 10-megawatt installations for utilities in New York and Washington State.
In December 2024, Form Energy achieved a crucial safety milestone when its iron-air battery system successfully completed UL9540A safety testing, demonstrating no flame or thermal event propagation even under extreme abuse conditions. This certification distinguishes Form’s technology from lithium-ion batteries and eliminates the need for fireproof barriers, simplifying installation and reducing costs. The company’s largest planned installation, an 8,500-megawatt-hour system in Lincoln, Maine, is scheduled to begin construction in 2027 and will be the largest battery project by energy storage capacity in the world when it comes online in 2028. With the ability to enable renewables to function as baseload power, Form Energy is positioned to play a pivotal role in the transition to a fully decarbonized electric grid.
5. Twelve: Converting Carbon Dioxide into Sustainable Products
Twelve, formerly known as Opus-12, represents an innovative approach to carbon reduction: instead of simply capturing carbon dioxide, the company transforms it into valuable products. Founded in 2015 and based in Berkeley, California, Twelve has developed a breakthrough technology that uses renewable energy to convert carbon dioxide, water, and air into sustainable chemicals and fuels through a process called carbon transformation. This approach not only reduces atmospheric carbon but also creates drop-in replacements for fossil fuel-based products, addressing emissions at their source.
The company’s technology platform has attracted partnerships with some of the world’s largest corporations. Alaska Airlines, BCG, Microsoft, and Shopify have all invested in or purchased Twelve’s products, validating both the technology and its commercial viability. Recently, Twelve opened a commercial-scale facility in Washington State that has begun production, marking a significant transition from pilot projects to full-scale manufacturing. The company’s initial focus has been on producing sustainable aviation fuel, one of the hardest-to-decarbonize sectors of the economy, where traditional electrification solutions are not feasible.
What makes Twelve particularly compelling is its ability to create carbon-negative products while generating economic value. The company’s electrochemical process uses renewable electricity to drive chemical reactions that would traditionally require fossil fuels and high temperatures. This approach can produce a wide range of products including sustainable aviation fuel, plastics, and other chemicals, all while permanently removing carbon dioxide from the atmosphere or preventing its release. In 2026, as industries face increasing pressure to decarbonize their supply chains and products, Twelve’s technology offers a practical pathway for companies in aviation, chemicals, and consumer goods to achieve their climate goals.
The company has raised significant venture funding and continues to expand its production capacity and product portfolio. Twelve’s carbon transformation platform demonstrates that addressing climate change can align with economic incentives, creating a sustainable business model that scales with demand. As carbon pricing mechanisms expand globally and consumer preference shifts toward sustainable products, Twelve is positioned to become a major player in the emerging carbon-to-value economy.
6. Calyxia: Tackling Microplastic Pollution at the Source
French cleantech innovator Calyxia is addressing one of the most pervasive environmental challenges of our time: microplastic pollution. These tiny plastic particles have infiltrated every corner of our planet, from the deepest oceans to our food supply and even our bodies. Unlike companies focused on cleaning up existing microplastic pollution, Calyxia takes a preventive approach by developing technology to produce microparticles and microcapsules using biodegradable materials that don’t leave harmful environmental footprints.
Founded with a mission to combat the microplastics that have become ubiquitous in rivers, soil, and human bodies, Calyxia has developed proprietary encapsulation technology that enables industries to transition away from petroleum-based microplastics. The company’s sustainable alternatives maintain the functional properties required by manufacturers while eliminating the long-term environmental harm associated with traditional microplastics. This technology has applications across multiple industries including cosmetics, agriculture, textiles, and consumer products, where microencapsulation is widely used for fragrance delivery, controlled release of active ingredients, and protective coatings.
In late 2025, Calyxia secured a $31 million Series B funding round to scale production and begin deploying its products to plastic manufacturers globally. The company aims to achieve profitability by 2026, a testament to both the market demand for sustainable alternatives and the commercial viability of its technology. Calyxia’s approach addresses microplastic pollution at its source, preventing billions of non-degradable particles from entering the environment rather than attempting to remove them after they’ve dispersed.
As regulatory pressure increases globally around microplastic pollution, with the European Union and other jurisdictions implementing bans and restrictions on certain uses, Calyxia’s technology provides manufacturers with compliant alternatives that maintain product performance. The company represents a new generation of material science startups that are fundamentally reimagining industrial processes to be compatible with planetary boundaries. In 2026, Calyxia is expanding its production capacity and forging partnerships with major manufacturers across multiple sectors, positioning itself as a leader in the transition toward biodegradable materials.
7. Aerones: Transforming Wind Turbine Maintenance with Robotics
As wind power capacity expands globally, maintaining these massive machines has become a critical challenge affecting both operational efficiency and project economics. Aerones, a Latvian company backed by Y Combinator, has developed a comprehensive robotics solution that addresses the costly and dangerous work of wind turbine maintenance. Founded in 2015, Aerones has achieved remarkable market penetration, currently supporting 50 percent of the world’s wind power capacity with its robotic systems.
The company’s technology encompasses multiple aspects of wind turbine servicing, including blade repair, cleaning, anti-freeze application, and inspection. Traditional maintenance methods require highly trained technicians to work at dangerous heights, often suspending them from ropes hundreds of feet in the air. Aerones’ robotic systems eliminate this risk while performing maintenance tasks 40 percent more efficiently than conventional methods. The robots can operate in weather conditions that would ground human workers, significantly reducing turbine downtime and increasing energy production.
In 2025, Aerones secured $30 million in growth capital to fuel its global expansion and continue developing its suite of robotic services. As the wind energy sector faces pressure to reduce costs and improve operational efficiency, Aerones’ technology offers a compelling value proposition. The company’s systems not only improve safety and reduce maintenance costs but also extend the operational lifespan of wind turbines through more frequent and thorough maintenance. With wind turbine blades growing larger—some now exceeding 100 meters in length—the complexity and importance of proper maintenance has increased proportionally.
In 2026, Aerones is expanding its geographic footprint and developing new robotic capabilities to address emerging maintenance challenges as wind turbine technology continues to evolve. The company exemplifies how robotics and automation can accelerate the clean energy transition by making renewable infrastructure more economical and reliable. As countries worldwide accelerate wind power deployment to meet climate targets, Aerones is positioned to become an essential service provider for the global wind energy industry.
8. Runwise: Optimizing Building Energy Efficiency Through AI
New York-based Runwise is tackling one of the most overlooked sources of energy waste: inefficient heating systems in commercial and residential buildings. The company has developed a unique hardware and software service that uses artificial intelligence to optimize heating systems, significantly reducing energy consumption, costs, and carbon emissions. Currently controlling heating systems in over 2,000 buildings throughout the Northeast United States, Runwise demonstrates how smart building technology can deliver immediate climate benefits while generating cost savings.
Buildings account for approximately 40 percent of global energy consumption and contribute substantially to greenhouse gas emissions, with heating systems representing a major portion of that energy use. Runwise’s approach combines IoT sensors, weather forecasting, and machine learning algorithms to precisely control boilers and heating systems, eliminating waste while maintaining occupant comfort. The company’s platform continuously learns from building performance data, optimizing operations in real-time based on factors including outdoor temperature, building occupancy, and energy prices.
What makes Runwise particularly valuable is its business model, which aligns incentives between the company and building owners. Rather than charging upfront for equipment and installation, Runwise operates on a services model where it shares in the energy savings it generates. This removes the capital expenditure barrier that often prevents building owners from investing in energy efficiency upgrades. The company handles installation, maintenance, and system optimization, providing building owners with immediate operational savings and reduced carbon footprints.
In 2026, as cities like New York implement increasingly stringent building emissions regulations and energy costs remain volatile, Runwise’s value proposition has strengthened considerably. The company is expanding beyond the Northeast into other markets and developing additional services for comprehensive building energy management. Runwise represents the convergence of artificial intelligence, IoT technology, and climate action, demonstrating how existing infrastructure can be dramatically improved through smart controls and data-driven optimization. With millions of buildings worldwide operating inefficient heating systems, Runwise’s technology offers a scalable pathway to reducing emissions in the built environment.
9. AMP Robotics: Revolutionizing Recycling with Computer Vision
AMP Robotics is applying artificial intelligence and computer vision to solve one of the waste industry’s most persistent challenges: sorting recyclable materials efficiently and accurately. Based in Colorado, AMP has developed robotic systems that use machine learning to identify and sort recyclable materials on conveyor belts with superhuman speed and accuracy. With hundreds of deployments across North America, Asia, and Europe, AMP’s technology is transforming the economics of recycling and enabling the recovery of materials that would otherwise end up in landfills.
Traditional recycling facilities rely on manual sorting, which is labor-intensive, expensive, and imprecise. Workers must identify and separate different types of plastics, metals, paper, and other materials as they rapidly pass by on conveyor belts—a difficult and often dangerous job. AMP’s AI-powered robots can process materials faster than human workers while maintaining consistent accuracy. The system’s computer vision can distinguish between dozens of material types and brands, enabling more sophisticated sorting that increases the value of recovered materials and reduces contamination.
The company’s technology delivers multiple benefits to waste and recycling operators. By reducing labor costs while increasing recovery rates, AMP’s systems improve the financial viability of recycling operations. The robots can work continuously without breaks, increasing throughput and operational efficiency. Additionally, the data collected by AMP’s systems provides insights into waste composition, helping facilities optimize their operations and municipalities understand their waste streams. This information is valuable for supply chain transparency and for companies seeking to improve product recyclability.
In 2026, as corporate sustainability commitments drive demand for recycled materials and extended producer responsibility regulations expand globally, AMP Robotics is positioned at the intersection of automation, artificial intelligence, and the circular economy. The company continues to refine its AI models and expand its deployment footprint, working with major waste management companies to increase recycling rates and reduce the environmental impact of waste. AMP demonstrates how advanced robotics can enable more sustainable resource management while creating economically viable business models in an industry that has historically struggled with thin margins.
10. PolyGone: Filtering Microplastics from Water Systems
Completing our list is PolyGone, a United States-based startup that has developed natural filtration technology to remove microplastics from water systems. As awareness of microplastic pollution has grown, particularly concerning their presence in drinking water and aquatic ecosystems, solutions for removing these contaminants have become increasingly urgent. PolyGone’s approach uses bio-based materials to create filters that can capture microplastic particles without relying on energy-intensive processes or generating toxic waste.
Microplastics pose a unique challenge because of their small size, varied composition, and ubiquitous presence in water systems ranging from municipal drinking water to industrial wastewater to natural waterways. Traditional filtration methods struggle to cost-effectively remove these particles, particularly at the scale required to make meaningful environmental impact. PolyGone’s natural microplastic filter technology offers a practical solution that can be integrated into existing water treatment infrastructure, providing an additional line of defense against this pervasive pollutant.
The company represents the emerging field of environmental remediation technology focused specifically on persistent pollutants that weren’t contemplated when most water treatment infrastructure was designed. As research continues to reveal the health impacts of microplastic ingestion and accumulation in ecosystems, regulatory requirements for microplastic removal are likely to expand. PolyGone’s technology positions the company to benefit from this regulatory trend while providing immediate environmental benefits.
In 2026, PolyGone is working to scale its production and secure partnerships with water utilities, industrial facilities, and municipalities seeking to address microplastic contamination. The company exemplifies how cleantech innovation is expanding beyond energy generation and storage to encompass broader environmental challenges. As public awareness of microplastic pollution increases and scientific evidence of health impacts strengthens, solutions like PolyGone’s will become increasingly essential components of water infrastructure.
Challenges and Opportunities Ahead
Despite remarkable progress, cleantech startups face significant challenges in 2026. Scaling production from pilot projects to commercial deployment requires substantial capital, and many technologies must prove they can maintain performance and cost targets at scale. Regulatory frameworks, while becoming more supportive in many jurisdictions, still create uncertainty, particularly for novel technologies like advanced nuclear and fusion that require new regulatory approaches. Supply chain challenges persist, especially for critical materials needed in batteries, clean energy infrastructure, and advanced manufacturing.
The competition for talent remains intense, with cleantech companies competing against technology giants for engineers, data scientists, and operations specialists. The need to simultaneously innovate on technology, manufacturing processes, business models, and regulatory approaches creates complexity that strains organizational capabilities. Additionally, the long development timelines inherent in hardware-intensive businesses test investor patience and require founders to maintain momentum through multiple funding cycles.
However, the opportunities are equally significant. Global energy demand continues to rise, driven by artificial intelligence, electrification of transportation, and economic development. Climate policies are becoming more stringent, creating stronger market signals for clean technologies. Corporate sustainability commitments are translating into procurement decisions and partnerships that provide stable demand for proven solutions. Financial markets are developing more sophisticated ways to value climate tech companies, moving beyond simple revenue multiples to consider the value of deployed capacity, long-term contracts, and strategic positioning.
The convergence of artificial intelligence with cleantech applications is creating new possibilities for optimization, automation, and system integration. Software-enabled hardware companies like Watershed, Runwise, and AMP Robotics demonstrate how digital tools can enhance physical systems and create defensible competitive advantages. The proliferation of sensors, connectivity, and computing power enables unprecedented visibility into energy systems, material flows, and environmental conditions, creating opportunities for data-driven optimization that were impossible a decade ago.
Conclusion: The Decade of Deployment
The cleantech startups profiled here are transitioning from promising concepts to deployed solutions addressing the climate crisis at scale. In 2026, we are entering what many observers call the decade of deployment, where technologies that have been developing for years begin operating commercially and delivering measurable climate benefits. The companies that succeed will be those that can navigate the complex challenges of scaling hardware, managing regulatory requirements, building supply chains, and maintaining the financial runway to reach profitability.
For investors, customers, policymakers, and anyone concerned about climate change, these companies represent both hope and opportunity. They demonstrate that technological innovation, properly supported and commercially deployed, can address environmental challenges while creating economic value. As these ten startups and their peers continue to grow and mature, they will play an essential role in determining whether humanity can successfully transition to a sustainable energy system and economy. The next few years will be critical in determining which technologies achieve widespread adoption and which companies emerge as the defining players in the cleantech revolution that will shape the remainder of the 21st century.
