Every energy & climate company Y Combinator has ever backed.

Uses machine learning models trained on geological datasets to identify high-probability uranium deposits — a critical input for the nuclear renaissance driven by AI data center demand. Shortens exploration cycles dramatically as uranium prices surge post-2022.

Sits between utilities and large power buyers, using AI to forecast pricing, optimize procurement timing, and navigate complex energy markets. As data centers triple their electricity demand through 2030, energy cost becomes a top-3 operating expense — making procurement intelligence high-value.

Builds AI models that respect physical laws governing fluid dynamics and thermodynamics, enabling far more accurate predictions of HVAC behavior than black-box neural nets. Can reduce cooling energy use by 20–40% with no hardware changes.

Repurposes retired electric vehicle battery packs (still holding 70–80% capacity) into grid-scale storage systems co-located with data centers. Controls the full stack from battery reconditioning to energy management software. Positioned at the intersection of AI infrastructure and circular battery economy.

Brings a browser-native, AI-assisted interface to grid planning — a process that today requires months of specialist engineering work in legacy software. As grids absorb distributed solar, wind, and storage at unprecedented speed, planning bottlenecks are becoming a national constraint.

Addresses the operational bottleneck at EV and AV depots: plugging in, repositioning, and readying vehicles for service. Robotic systems autonomously handle charging and staging workflows, enabling depot operators to run leaner teams with higher throughput.

Combines market price forecasting with battery dispatch optimization, enabling owners of utility-scale storage assets to maximize revenue in volatile wholesale electricity markets. Battery storage is increasingly the swing asset in power markets, and Dartboard automates what was once manual trading-desk work.

Targets one of the hardest-to-decarbonize sectors — deep-sea shipping — with compact fusion reactor systems designed for onboard use. Ships represent ~2.5% of global CO2 emissions and have very few viable decarbonization pathways.

Solves one of the biggest bottlenecks in renewable energy deployment: finding viable grid interconnection points. Maps available capacity across the grid and matches it with land and permitting data, dramatically shortening the pre-development phase for solar and wind projects.

Developing compact fusion reactors for deployment in space — where weight, reliability, and power density are paramount. As satellites, orbital stations, and lunar infrastructure scale, power generation becomes a critical constraint.

Targets the emissions-intensive heavy industries (mining, oil & gas, cement) that generate the bulk of global industrial CO2. Connects siloed operational data sources and automates compliance workflows including emissions reporting, regulatory filings, and ESG disclosures.

Continuously decides when to charge (buying cheap power) and when to discharge (selling into high-price periods or providing grid services). Improves asset revenue by 15–30% vs. manual or rule-based dispatch. As battery storage deployments accelerate globally, the optimization software layer becomes critical infrastructure.

Provides battery scientists with a software environment to simulate and test cell designs before building physical prototypes — dramatically compressing the development cycle. Replaces months of wet-lab iteration with fast digital experiments.

Finances, installs, and operates solar and battery systems for commercial real estate owners without capital expenditure. Similar to residential solar PPAs but targeted at commercial and industrial customers. Retains system ownership and sells power at a discount to utility rates.

Aggregates satellite imagery, permitting data, grid capacity maps, environmental constraints, and land use data into a single platform for renewable energy developers. Compresses multi-month desktop studies into days.

Builds large-scale ML models trained on decades of Earth observation and atmospheric data to simulate physical systems. Accurate weather modeling is foundational to energy grid management, agriculture, insurance, and disaster response.

Deploys long-endurance aerial platforms carrying atmospheric sensors to continuously sample weather data at altitudes and locations underserved by existing observation networks. Serves aviation, energy grid operators, agriculture, and government meteorology.

Connects to utility accounts across hundreds of providers and automatically ingests, normalizes, and analyzes energy consumption data. Energy managers today spend 70% of their time on manual data collection; Nectar automates this entirely and layers AI-driven insights on top.

Improves the effective capacity and cycle life of grid-scale battery storage systems by optimizing charge/discharge algorithms at the electrochemical level. For a 100 MWh battery asset, safely recovers 10–20 MWh of additional revenue-generating capacity with no hardware spend.

Solar and hydrogen-powered airships fly for days along gas pipelines and power transmission corridors, continuously scanning for methane leaks and electrical faults. Replaces expensive manned helicopter inspections with persistent, low-cost autonomous monitoring.

Manufactures and deploys advanced metering infrastructure with integrated analytics, enabling utilities to move from estimated billing to real-time consumption data and anomaly detection. Enables time-of-use pricing programs as variable renewables grow.

Aggregates and visualizes utility interconnection queue data, substation capacity, and transmission constraints into a single map. Used by major developers including AES and Cypress Creek. Grid interconnection has become one of the primary bottlenecks to renewable energy deployment in the US.

Solves the "split incentive" problem in real estate solar: landlords own the roof but tenants pay the electricity bill. Enables peer-to-peer energy transactions between landlord solar systems and tenant meters, creating new revenue for building owners and lower bills for tenants.

Provides modular, containerized battery storage and backup power systems that can be deployed in days rather than months, with no upfront capital (PaaS model). As extreme weather events increase grid outages and electricity prices grow more volatile, resilient behind-the-meter power is becoming a board-level issue.

Developing direct air capture technology powered by renewable energy, with a design intended to scale manufacturing like a commodity product. Raised $6.9M seed backed by Alumni Ventures and ENEOS Holdings (Japan's largest energy company). Partnered with geothermal energy producers to leverage cheap clean power.

Installs onboard carbon capture equipment intercepting exhaust gases and converting CO2 into calcium carbonate — a stable solid offloaded at port. Backed by Lowercarbon Capital and Eastern Pacific Shipping. Received £1.1M grant from UK government in 2025 for port-side carbon capture at Southampton.

Builds AI-powered AUVs that selectively harvest battery-critical metals (nickel, cobalt, manganese) from the ocean floor without dredging. Has $500M+ in off-take LOIs and is planning a $1B+ fundraise in 2026. Has a permit application sponsored by the Kingdom of Bahrain.

Develops algae-derived feed additives that inhibit methane-producing archaea in the digestive systems of ruminant livestock. Enteric fermentation accounts for ~5% of global greenhouse gas emissions — a massive and largely unaddressed source.

Uses engineered microorganisms to ferment CO2 captured from industrial processes into high-value chemicals like ethanol and acetone — creating a circular carbon economy. At scale, gas fermentation could become one of the most cost-effective forms of both carbon utilization and renewable chemical production.

Replaces asphalt with lignin — a byproduct of wood pulp processing — as the binding agent in road surfaces. Crushes existing road material in place and re-binds it with lignin, eliminating new asphalt and capturing carbon in the road itself. Makes roads cheaper, stronger, and carbon-negative.

Building electric short-sea cargo vessels for US coastal and inland waterway routes. Claims $100M+ in preliminary sales commitments. Electric ships on short routes are economically viable today. Targets the Jones Act market, where US-built and US-operated ships are legally required.

Uses synthetic biology and machine learning to design enzymes that break down PET plastic into its base monomers at commercially viable speeds and temperatures. The resulting monomers can be used to make virgin-quality recycled plastic, closing the loop on plastic waste.

Built software that aggregates and orchestrates the flexible load capacity of commercial buildings — HVAC, lighting, EV chargers, and battery storage — into virtual power plant programs that utilities can call on during peak demand. Acquired as utilities race to build demand flexibility programs.

Built MRV software for forest carbon projects using satellite imagery and ML models to verify forests are storing the carbon they claim. Merged with Tree.ly to create a larger European forest carbon platform as demand for high-quality, verifiable carbon credits grows.

The "Plaid" of the energy hardware world — a universal API that lets developers query and control any energy device through a single standardized interface, regardless of manufacturer. Enables a new generation of demand response, EV smart charging, and energy optimization applications.

Builds EV chargers designed for multi-family buildings and parking garages, working via Bluetooth-based authentication. Enables EV charging installation in older apartment buildings that dominate European cities — addressing the "charging at home" gap that holds back EV adoption for non-homeowners.

Purpose-built for fashion brands, ingesting supply chain data to calculate product-level carbon footprints with Scope 1, 2, and 3 coverage. Serves 200+ brands including The North Face, Columbia, Allbirds, and Carhartt. EU regulations are making emissions disclosure mandatory, driving rapid adoption.

Direct air capture technology using electrochemical reactions powered by renewable electricity to pull CO2 from air and mineralize it permanently in rock — achieving one of the most durable forms of carbon removal. Backed by Sam Altman and Marc Benioff.

A marketplace and advisory platform that helps companies source high-quality carbon credits. Publishes widely-cited research on voluntary carbon market pricing and quality trends. Backed by YC, BlueBear Capital, and Global Founders Capital. The voluntary carbon market saw $16.3B in project financing in 2024.

Deploys robotic seaweed cultivation platforms in the open ocean, growing fast-reproducing macroalgae and sinking it to depths greater than 1,500m where the carbon is sequestered for 1,000+ years. Ocean-based carbon removal is among the most scalable and lowest-cost theoretical pathways.

Built software that aggregates the flexible electricity demand of commercial buildings and responds to price signals from the Nordic spot market in real-time. Automatically pre-heats or pre-cools buildings when electricity is cheap and reduces consumption when prices spike. Acquired.

Operates a battery-as-a-service network for electric three-wheelers and light commercial vehicles in India, enabling drivers to swap depleted batteries for fully charged ones in minutes. Eliminates the battery upfront cost (the largest component of EV price) and enables high-utilization commercial vehicles to run continuously.

Was developing cultivated (lab-grown) beef using proprietary cell line optimization and bioreactor techniques to produce meat products without slaughter. Acquired, joining the wave of consolidation in the cultivated meat sector as the industry faces commercialization hurdles.

Builds direct liquid cooling systems that circulate coolant directly through server components. As AI chips run hotter (Nvidia H100s dissipate 700W each), air cooling is becoming physically insufficient for dense GPU clusters. DLC systems can reduce cooling overhead from 30–40% of total power to under 5%.

Helps carbon-intensive corporations model internal carbon prices, track Scope 1-3 emissions, and build actionable decarbonization roadmaps. Named a market leader in carbon management by Verdantix in August 2025. Serves global enterprises facing mandatory disclosure under CSRD, SEC climate rules, and ISSB standards.

Builds digital twin and state estimation software for lithium-ion batteries deployed in EVs, stationary storage, and industrial applications. Continuously models battery state-of-health, remaining useful life, and safety thresholds using physics-based models combined with real operational data.

Operates a nationwide EV charging network in India, targeting highways, malls, hotels, and workplaces. Raised $45.5M from Shell Ventures, YC, and others. In 2026, raised an additional $18M to scale to 20,000 chargers. India's EV market is one of the fastest-growing globally.

Provides SMBs with an accessible carbon accounting platform that connects to accounting software and other data sources to automatically estimate Scope 1 and 2 emissions. Targets the large underserved market of small and medium businesses facing growing customer and investor pressure.

Focuses on Scope 3 emissions embedded in physical commodity supply chains (metals, fuels, agricultural products). Connects to trade data and production records to calculate the carbon intensity of commodities as they move through the supply chain. Banks and commodity traders are primary customers.

Trains ML models on geological survey data, historical drilling records, and geophysical data to identify where critical minerals are most likely to be found. Less than 1 in 1,000 targets becomes a producing mine — StratumAI helps exploration companies prioritize the highest-potential targets.

Uses precision breeding and genetic engineering to develop tree varieties that photosynthesize more efficiently and store more carbon per tree. Enhanced poplar trees grow 53% faster than wild-type. Sells carbon credits from planted forests. Planted on 12,000+ acres as of 2024.

Built hardware-software systems providing building operators with real-time, circuit-level energy monitoring — going beyond smart meters to show exactly which systems are consuming power and when. Acquired, likely by a building management or energy management platform.

Uses proprietary carbon nanotube membranes to capture CO2 from ambient air and electrochemically convert it into hydrocarbon fuels — running combustion in reverse using renewable electricity. The resulting fuels are drop-in replacements for conventional jet fuel and ship fuel.

Autonomous aircraft tethered to the ground fly in figure-eight patterns to generate electricity through tether motion — accessing stronger, more consistent winds at altitude without a tower. Uses 10x less materials than a conventional turbine. Connected the first system to the public grid in Germany.

Calculates users' personal carbon footprints and enables them to fund a curated portfolio of carbon offset projects spanning nature-based solutions, direct air capture, and clean cooking. Emphasizes transparency with detailed project tracking and verification.

Built an MRV platform for forest carbon using satellite imagery, LiDAR, and ML models to independently verify that forests are actually storing the carbon they claim. Used by Shopify, American Express, and Microsoft. Acquired by Carbon Direct in November 2025.

Uses ML models trained on geological, geochemical, and geophysical data to identify drill targets for critical minerals needed in the energy transition (copper, nickel, lithium, cobalt, rare earths). Makes probabilistic predictions about where mineralization is most likely to occur.

Developed an electrochemical process that uses renewable electricity to convert CO2 into solid graphite — permanently removing carbon from the atmosphere while producing a valuable material used in lithium-ion battery anodes. Carbon-negative while generating a revenue-positive product.

Develops hydrofoil systems that lift ship hulls out of the water, dramatically reducing drag and fuel consumption for ferries and workboats. At speed, a hydrofoil ship consumes 80–90% less energy than a displacement hull, enabling electric propulsion on previously too energy-intensive routes.

Builds large tethered drones and robotic climbing systems that service wind turbine blades — replacing dangerous manual rope-access work with automated, safer, faster operations. Customers include GE, Siemens Gamesa, and Vestas. Market leader in robotic turbine servicing.

Developing thermodynamic machines based on advanced Stirling cycle technology for industrial heat pumps and long-duration seasonal thermal energy storage. Industrial heat represents ~20% of global CO2 emissions. Systems can deliver heat at 200–400°C using electricity, enabling full electrification of industrial heating.

Engineers nanostructured silicon particles used as anode material in lithium-ion batteries, enabling significantly higher energy density compared to conventional graphite anodes. Silicon anodes can theoretically store 10x more lithium than graphite. Targets US-produced battery materials.

Converts palm kernel shells — a high-volume agricultural waste product from West African palm oil processing — into biochar through pyrolysis. When added to soil, the carbon is stably sequestered for hundreds of years while improving soil fertility. Sells carbon removal credits generated.

Developed a liquid-applied battery separator that replaces the thin film between battery electrodes in lithium-ion cells. Applied at room temperature, dramatically reducing manufacturing complexity and defect rates. The ceramic-composite separator has superior thermal properties, reducing the risk of thermal runaway.

Provides oil and gas producers, midstream operators, and traders with real-time measurement and verification of hydrocarbon quality and emissions calculation. Raised $68.6M total including a $43M Series B led by Mercuria Energy and BlackRock. Hit $16.5M ARR in 2024.

Builds clamp-on ultrasonic sensors that measure flow, composition, and anomalies in pipes without requiring any pipe penetration or process shutdown. Used in oil & gas, water utilities, and chemical plants to detect leaks, monitor product quality, and optimize operations.

Provides affordable solar energy to households without access to reliable electricity in Nigeria and other African markets through a pay-as-you-go financing model. Customers pay small daily amounts via mobile money, removing the barrier of large upfront costs for solar installations.

The SolarCity equivalent for Mexico — a software and finance platform enabling solar installers to offer rooftop solar to homeowners with no upfront cost. Backed by Leonardo DiCaprio, JB Straubel (Tesla co-founder), and First Round Capital. Raised $59M+ total.

Combines solar installation with flexible financing models to bring clean electricity to institutions in Nepal and other developing countries that cannot afford grid connections or diesel generators. Has enabled schools and health clinics to access reliable electricity for the first time.

Developing technology to transmit electrical power wirelessly over meaningful distances — enabling charging of sensors, IoT devices, and small electronics without physical connectors or batteries. Applications in hard-to-wire industrial monitoring, agricultural sensors, and infrastructure inspection.

Provided high-quality solar home systems to rural households in Senegal with no grid connection. PAYG model allowed customers to pay in small daily increments via mobile money. With 230 employees at acquisition, one of the larger YC climate companies. Acquired by a larger off-grid solar platform.

Started with AI-driven battery management software that accelerates li-ion charging without degrading cycle life. Pivoted in 2023 to developing their own lithium-metal battery — a next-generation chemistry with higher energy density. Demonstrated ~430 cycles at 1C charge/discharge rate for a Li-metal cell.