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Green hydrogen

Green hydrogen hydrogen colours Electrolysis renewable energies additionality power-to-gas storage Industry

Green hydrogen is hydrogen produced by electrolysis of water. The electricity used for this comes from renewable energy sources. Chemically, green hydrogen is no different from other hydrogen. An H₂ molecule stays the same whether it was obtained from natural gas, coal, biomass or water. The colour describes only the production route and thus the greenhouse gas balance. "Green" here is a term from everyday and technical language, not a legal term. In EU law, the corresponding category is called "renewable fuels of non-biological origin", abbreviated RFNBO. Precise rules on the origin of the electricity apply to this category.

In electrolysis, water is split into hydrogen and oxygen using electrical energy. As a rough guide, today's plants need about 50 to 55 kilowatt-hours of electricity per kilogram of hydrogen, depending on technology, age and mode of operation. In addition, energy is needed for compression, storage, transport or further processing. One kilogram of hydrogen contains about 33 kilowatt-hours of chemical energy, measured by the lower heating value. So roughly a third of the electricity input is already lost during production. Green hydrogen is therefore not a substitute for electricity. It is a way of converting electricity into a storable chemical energy carrier.

Production route and hydrogen colours

The common hydrogen colours classify hydrogen by how it is produced. Grey hydrogen is usually made from natural gas by steam reforming. The CO₂ released in the process generally enters the atmosphere. Blue hydrogen is also made from fossil raw materials, but part of the CO₂ is meant to be captured and stored. Turquoise hydrogen is produced by methane pyrolysis. This yields solid carbon, provided that process energy and permanent binding of the carbon are suitably organised. Green hydrogen starts from renewable electricity and water. Hydrogen from biomass is also sometimes colloquially called "green". Legally, however, it does not count as RFNBO in the EU because it is of biogenic origin.

This colour logic makes communication easier but does not replace a precise balance. The statement "renewable electricity" alone says little about climate impact. An electrolyser can draw electricity from a grid with a high fossil share and merely buy green electricity certificates on paper. It can then cause considerably more emissions than the term suggests. The European Commission expressly states that hydrogen from fossil-generated electricity has a substantially higher emission intensity than hydrogen conventionally produced from natural gas.

EU rules: additionality, temporal and geographical correlation

Binding criteria have emerged in the EU from this problem. They are set out in Delegated Regulation (EU) 2023/1184. Originally it applied to fuels in transport. Since the amendment by Delegated Regulation (EU) 2024/1408, it applies to renewable fuels of non-biological origin as a whole. The rules also apply to hydrogen that is produced outside the EU and is to be counted. Electricity from a directly connected renewable installation is considered fully renewable under certain conditions. The installation must have started operation no earlier than 36 months before the electrolyser, and no grid electricity may flow in. There are several routes for grid electricity:

  • Bidding zones with a very high share of renewable electricity: If the renewable share in the previous year was above 90 percent, grid electricity may count as renewable. The number of operating hours is then limited to this share.

  • Bidding zones with very clean electricity: If the emission intensity is below 18 g CO₂ equivalent per megajoule, additionality does not apply. However, purchase contracts for renewable electricity as well as temporal and geographical correlation are then required.

  • Redispatch: Grid electricity can count as renewable if the electrolyser has demonstrably reduced the curtailment of renewable installations within the framework of redispatch.

  • All other cases: Here additionality, temporal correlation and geographical correlation must all be met together.

Additionality has a narrow meaning in EU law. The electricity must come from own installations or, via purchase contracts, from renewable installations. These must have started operation no earlier than 36 months before the electrolyser and, as a rule, must not have received operating or investment aid. The use of electricity that would otherwise have been curtailed does not fall under additionality. There is a separate redispatch route for this. Details are explained in the entry additionality criterion for green hydrogen.

On temporal correlation: until 31 December 2029, it is sufficient if hydrogen and contractually purchased renewable electricity are produced in the same calendar month. From 1 January 2030, the same hour is required. Member States may introduce hourly matching for their territory as early as 1 July 2027. Irrespective of this, temporal correlation is always deemed fulfilled if the day-ahead price in the bidding zone is at most 20 euros per megawatt-hour. The same applies if it is below 0.36 times the CO₂ allowance price. On geographical correlation: the generating installation must in principle be located in the same bidding zone as the electrolyser. Exceptions exist under price conditions for interconnected zones and for certain offshore bidding zones.

There is a transitional rule for early projects. Electrolysers that start operation before 1 January 2028 only have to meet additionality from 1 January 2038. The rules are currently under review. In spring 2026, the Commission announced a targeted revision, earlier than originally planned. Several Member States and industry associations are calling for the transitional periods to be extended to around 2035. Environmental organisations, by contrast, stand by the criteria as protection against higher emissions. As of November 2026, the revision had not yet been completed according to the sources reviewed. The deadlines mentioned therefore reflect the version currently in force and may change.

Distinction from green electricity, power-to-gas and storage

Green hydrogen is often equated with green electricity. This equation obscures the conversion losses. Electricity can be used directly in a motor, a heat pump or an industrial process. If it is first converted into hydrogen, then stored, transported and later converted back into electricity or heat, the usable yield falls significantly. In reconversion to electricity via fuel cells or gas turbines, usually only about a third to two fifths of the electricity originally used remains.

Power-to-gas is the umbrella term for processes that convert electricity into gaseous energy carriers. Green hydrogen is one form of it. Synthetic methane can be produced from hydrogen and CO₂. This also counts as power-to-gas but is no longer hydrogen. Such follow-on products can use existing infrastructure. However, they entail further conversion steps and losses.

As storage, green hydrogen is of interest above all for long periods. Batteries are well suited for minutes, hours and in part days. Hydrogen, by contrast, can balance differences between the seasons, provided large stores such as a salt cavern are available. Its strength lies less in the daily shifting of small amounts of electricity. It is better suited to covering rare, prolonged gaps in wind and solar power. It also supplies applications that need molecules as a raw material.

Role in the power system and in industry

Green hydrogen links the power system with sectors that have so far depended heavily on fossil energy carriers. In steelmaking, hydrogen can act as a reducing agent, converting iron ore into iron and replacing coal. The chemical industry needs hydrogen for ammonia, methanol and other basic materials. Refineries already consume large quantities today, which are mostly produced from fossil sources. Synthetic fuels for aviation and shipping can also be based on green hydrogen. This makes sense above all where direct electrification is difficult.

A large supply of hydrogen therefore does not arise independently of the power system. Electrolysers increase electricity demand. They compete for renewable generation, grid connections, land, water, capital and flexibility. What matters is therefore not only how much hydrogen is needed. Equally important is at which hours and in which places it can be produced and which applications should use it first.

Flexibly operated electrolysers can help the power system. They reduce their output when electricity is scarce or expensive, and produce more when plenty of wind or solar power is available. However, this does not happen automatically. Many plants have to run around the clock to cover investments or fulfil supply contracts. For the power system they are then simply an additional constant load. Flexible operation requires suitable technical design, intermediate storage, suitable contracts and market rules. The future hourly matching in the EU expressly requires that production follows the supply of renewable electricity.

Typical misconceptions

A common misconception: surplus green electricity will in future be available free of charge in large quantities for hydrogen. It is true that curtailment of wind and solar installations occurs, above all during grid bottlenecks. However, these quantities are neither reliable nor large enough for an entire hydrogen economy. Electrolysers need a minimum utilisation for the investment to pay off. If they run only a few hours a year, the hydrogen becomes expensive.

For building heating, the heat pump is considerably more efficient in most cases. If green electricity is first converted into hydrogen and then burned in a boiler, each unit of heat needs a multiple of that in electricity. In transport, fuel cells can make sense for certain heavy commercial vehicles or special applications. For passenger cars, the battery is more favourable in energy terms. Green hydrogen thus complements electrification where direct use of electricity reaches its limits. It is not a general replacement for it. The term becomes problematic when it is used to justify fossil infrastructure. An installation may well be "hydrogen-ready". But it does not follow that enough green hydrogen will be available at the site in time.

Costs, responsibility and security of supply

Costs consist of several items: electricity, investment in the electrolyser, operating hours, grid charges and connection, water treatment, compression, transport, storage and, where applicable, further processing. The proof and certification rules also affect costs because they co-determine electricity sourcing and operating times. Low electricity prices alone are therefore not enough. Green hydrogen becomes economic where generation, infrastructure and demand are planned together. Responsibility is spread across many levels. Electricity market rules, grid regulation, EU proof rules, funding policy and energy partnerships for imports interlock.

For security of supply, green hydrogen can become important in rarely running power plants. Such plants provide firm capacity when little wind and solar power is available and load is high. Their fuel requirement remains limited relative to total electricity consumption. However, this requires storage, power plant capacity, a suitable market design and clear funding of standby readiness. Overall, the term is precise when it discloses the production route and the origin of the electricity. It becomes imprecise when it presents hydrogen across the board as climate-neutral while ignoring conversion losses, scarcity and proof rules.

Sources

Related glossary entries

Edited by eCMS on 12.11.2026 05:05

© 2026 Erik Schmidt. All rights reserved. Quotations with a link to the source are welcome.