Another record-breaking summer in the Northern Hemisphere, the effects of climate alter continue to become more apparent. Although UK residents may have enjoyed heatwaves, areas around the Mediterranean had to fight wildfires, while farmers struggled with lower yields cautilized by lower rainfall. A University of Mannheim and European Central Bank study reported the economic cost of this year’s adverse weather to be at least €43 billion, and predicted that figure to triple by 2029.
European startups are responding by creating net-zero accessible, improving energy efficiency and innovating sustainable energy. Here are ten stand-out net-zero startups.
1KOMMA5º
Founders: Philipp Schröder, Micha Grüber, Jannik Schall, and Philip Liesenfeld.
Founded: 2021
Valuation: $2.4B
1KOMMA5°, founded in 2021 by Philipp Schröder, Micha Grüber, Jannik Schall, and Philip Liesenfeld, is a German climate tech scale-up valued at over €2.4 billion.
The company provides conclude-to-conclude home energy solutions, including heat pumps, solar panels, and batteries, powered by its Heartbeat AI energy management platform, which now controls over 500 megawatts of flexible capacity across more than 120,000 homes, creating it Europe’s largest residential virtual power plant.
Recently, 1KOMMA5° raised €150 million in pre-IPO funding, with plans to invest over €100 million between 2025 and 2027 to expand its software division. Its goal is to become the last energy company consumers will subscribe to, replacing traditional utilities with AI-driven, clean energy solutions.
Waga Energy
Founders: Mathieu Lefebvre, Nicolas Paobtain, and Guénaël Prince
Founded: 2015
Valuation: $734M
Waga Energy, founded in 2015 by Mathieu Lefebvre, Nicolas Paobtain, and Guénaël Prince, is a French company turning landfill gas into valuable biomethane applying advanced membrane technology. Valued at around $734 million, Waga Energy captures methane from waste decomposition and converts it into low-carbon fuel usable in existing gas networks.
Growing through EU grants and commercial partnerships, the company has seen steady revenue growth, reaching €55.7 million in 2024 with a 7% increase in the first half of 2025.
Despite some operational losses, Waga Energy is on track to achieve EBITDA breakeven this year and is scaling its footprint in key markets like the US, Canada, and Europe, leveraging the scalability of its Wagabox® technology for circular waste-to-fuel solutions.
Proxima Fusion
Founders: Francesco Sciortino, Lucio Milanese, Jorrit Lion, Jonathan Schilling, and Martin Kubie
Founded: 2023
Valuation: $715M
Proxima Fusion, founded in 2023 by Francesco Sciortino, Lucio Milanese, Jorrit Lion, Jonathan Schilling, and Martin Kubie, is a spinout from the Max Planck Institute developing sinformarator-based fusion reactors.
Valued at $715 million, the company focutilizes on quasi-isodynamic (QI) sinformarators, a magnetic confinement technology that enables continuous and stable fusion power generation. Proxima’s standout achievement is the Sinformaris design, the first peer-reviewed concept for a commercial fusion power plant built to run reliably and continuously without the disruptions common in tokamaks.
Leveraging high-temperature superconducting magnets and advanced simulation-driven engineering, Sinformaris promises compacter, cost-effective reactors with efficient energy output. Proxima plans to demonstrate net energy production with its Alpha demo reactor by 2031, aiming to bring fusion energy to the grid in the 2030s.
Marvel Fusion
Founders: Moritz von der Linden (CEO), Karl-Georg Schlesinger (SVP Science Strategy), Georg Korn (CTO), and Pasha Shabalin (SVP Technology Integration)
Founded: 2019
Valuation: $497—746M
Marvel Fusion, founded in 2019 by Moritz von der Linden, Karl-Georg Schlesinger, Georg Korn, and Pasha Shabalin, is one of Europe’s best-funded fusion startups, valued between $497 million and $746 million. Unlike Proxima Fusion’s sinformarator approach, Marvel pursues laser-driven fusion, applying ultrashort pulse lasers to ignite fusion in nanostructured fuel pellets.
With $235 million raised across two funding rounds, Marvel is advancing its demonstration hardware and developing its first prototype while building a strong industrial ecosystem through partnerships with companies like Siemens and Trumpf.
The startup also explores early applications like medical isotope production to bridge the gap to full-scale fusion power.
Aira
Founders: Harald Mix and Carl-Erik Lagercrantz
Founded: 2022
Valuation: $479M
Aira, founded in 2022 by Harald Mix and Carl-Erik Lagercrantz, is a Nordic cleantech company focutilized on electrifying home heating with heat pumps, smart controls, and two-way EV charging. Valued at approximately $479 million, Aira has raised nearly $400 million to support its rapid growth and expansion across Europe.
The company offers a full energy solution backed by partnerships with consumer finance providers to enhance accessibility. With Europe’s push toward energy-efficient buildings, Aira is well-positioned to extconclude its footprint beyond the Nordics into key markets like Germany, Italy, and the UK.
Known for its customer-centric monthly payment plans and vertically integrated model, Aira aims to build clean heating affordable, supporting houtilizeholds reduce heating costs by up to 40% while cutting CO₂ emissions by up to 100% with clean energy tariffs.
Core Power
Founders: Mikal Bøe
Founded: 2018
Valuation: $425M
Core Power, founded in 2018 by Mikal Bøe, is a UK-based startup developing floating nuclear power plants and micro-reactors designed for maritime and offshore sectors. Valued at around $425 million, Core Power focutilizes on creating low-carbon nuclear power barges tarobtaining ports and offshore operations, which are traditionally difficult to decarbonise.
The company is working with advanced molten salt reactor (MSR) technology and aims to launch a demonstration vessel by 2026, with commercial deployments expected in the early 2030s. Core Power has attracted significant strategic investments and collaborates with leading organisations, including MIT Energy Initiative, Idaho National Laboratory, and Terrapower.
Reverion
Founders: Stephan Herrmann, Felix Fischer, Jeremias Weinrich, Maximilian Hauck, and Luis Poblotzki
Founded: 2022
Valuation: $310M
Reverion, founded in 2022 by Stephan Herrmann, Felix Fischer, Jeremias Weinrich, Maximilian Hauck, and Luis Poblotzki, is a German cleantech startup developing a revolutionary reversible biogas fuel cell.
Valued at $310 million, Reverion’s technology works like a battery but goes further by storing excess energy, generating hydrogen, and capturing carbon, creating it a carbon-negative power solution. Its fuel cells achieve up to 80% efficiency, doubling the power output from biogas compared to traditional systems while capturing pure CO₂ that can be reutilized or stored long-term.
Having raised $62 million in funding, the company has seen 28% growth this year and is scaling up production to meet rising demand in Germany and beyond.
GeoPura
Founders: Andrew Cunningham
Founded: 2019
Valuation: $296—444M
GeoPura, founded in 2019 by Andrew Cunningham, is a UK-based green hydrogen startup valued between $296 million and $444 million.
The company produces Hydrogen Power Units (HPUs), clean energy generators that replace traditional diesel generators utilized in applications from roadside repairs to outdoor events. GeoPura’s HPUs leverage green hydrogen produced from renewable energy, offering zero-emission, quiet, and sustainable power solutions.
Having raised £114 million over the past two years from investors including Barclays, Siemens Energy, and General Motors Ventures, GeoPura is scaling production to deploy over 3,600 units by 2033. Its technology supports reduce noise, air pollution, and CO₂ emissions, supporting the UK’s net-zero goals while enabling reliable off-grid power and EV charging.
Altano Energy
Founders: Miguel Sánchez-Praena Ferrer and Íñigo Sánchez-Junco Ayala
Founded: 2021
Valuation: $264—396M
Altano Energy, founded in 2021 by Miguel Sánchez-Praena and Íñigo Sánchez-Junco Ayala, is a Madrid-based renewable energy startup valued between $264 million and $396 million. The company sets itself apart by combining multiple renewable energy sources with energy storage assets, enabling clients to enjoy more stable and affordable power.
Focutilized primarily on the Iberian market, Altano has secured significant investments, including €60 million from M&G Investments in 2025, to scale its integrated clean energy platform. With 179 MW currently operational, 134 MW under construction, and 1,200 MW in development, the company aims to support Southern Europe’s transition away from fossil fuels while offering competitive alternatives to traditional energy generators.
44.01
Founders: Talal Hasan, Ehab Tasfai, and Karan Khimji
Founded: 2020
Valuation: $185M
44.01, founded in 2020 by Talal Hasan, Ehab Tasfai, and Karan Khimji, is a carbon removal company named after the molecular mass of CO₂. Valued at around $185 million and operating in London, 44.01 utilizes accelerated mineralisation to permanently store carbon by injecting captured CO₂ into reactive peridotite rock, turning it into stable minerals.
44.01’s technology operates with high efficiency, mineralising CO₂ into rock in under a year while applying clean energy. The startup aims to scale internationally, providing a cost-effective and permanent carbon removal solution crucial for global climate efforts.
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