Green hydrogen
Hydrogen produced by splitting water in an electrolyser powered by renewable electricity, with near-zero direct CO2 emissions.
Green hydrogen is made by electrolysis: 2 H2O → 2 H2 + O2. Hydrogen carries 33.3 kWh/kg (LHV) or 39.4 kWh/kg (HHV), and splitting water requires at least 39.4 kWh/kg in theory. Real electrolyser systems consume 50–55 kWh/kg, a system efficiency of 60–67% on an LHV basis, plus about 9–10 litres of purified water per kg of H2.
Electricity dominates cost: at USD 30/MWh the power component alone is about USD 1.6/kg. With 2024 system capex of USD 1,700–2,500/kW for installed projects outside China (IEA Global Hydrogen Review) and capacity factors of 40–60%, levelised cost is typically USD 4–8/kg, compared with USD 1–2.5/kg for grey hydrogen. Chinese alkaline systems are 50–70% cheaper.
Under EU rules (Delegated Act 2023/1184), renewable hydrogen must meet additionality, temporal correlation (monthly, hourly from 2030) and geographic correlation requirements, and achieve at least 70% lifecycle savings, around 3.4 kg CO2e/kg H2 maximum. Global installed electrolysis capacity was only about 2–3 GW in 2025, far below announced plans. Model costs with the green hydrogen calculator.
Related terms
All terms →- Electrolyser
An electrochemical device that uses electric current to split water into hydrogen and oxygen; the core equipment of green hydrogen production.
- Blue hydrogen
Hydrogen produced from natural gas by reforming, with most of the resulting CO2 captured and permanently stored.
- Grey hydrogen
Hydrogen made from natural gas by steam methane reforming without carbon capture; the dominant and cheapest production route today.
- E-fuels (power-to-X)
Synthetic fuels made from electrolytic hydrogen, sometimes combined with captured CO2 or nitrogen, such as e-methane, e-methanol, e-kerosene and e-ammonia.
- Ammonia as fuel
Use of ammonia (NH3), a carbon-free hydrogen carrier, as a fuel for ships, power plants and long-distance hydrogen transport.
- Fuel cell
An electrochemical device that converts the chemical energy of hydrogen or another fuel directly into electricity and heat, without combustion.