Green Hydrogen Explained: Costs, Efficiency and Where It Makes Sense

Hydrogen has been the “fuel of the future” for half a century. Two things are new. Renewable electricity is now cheap enough to make it without fossil fuels, and industries with few other ways to cut emissions (steel, fertiliser, shipping) need a clean molecule. Hydrogen has also been oversold for jobs that direct electrification does better. To judge it, you need three numbers in your head: how much energy it takes to make, what it costs, and where it sits on the “hydrogen ladder” of uses.

Today’s hydrogen is not green

The world uses roughly 95–100 million tonnes of hydrogen a year (IEA, Global Hydrogen Review 2024). Nearly all of it goes into oil refining, ammonia and methanol production, and steel. Over 99% is made from fossil fuels:

Colour	Production route	Typical emissions (kg CO₂e/kg H₂)	Share today
Grey	Steam methane reforming (SMR) of natural gas	10–12 (more with methane leakage)	Majority
Brown / black	Coal gasification (mostly China)	18–25	Large share in China
Blue	SMR or autothermal reforming + carbon capture	2–5 (depends on capture rate and leakage)	Small
Green	Water electrolysis with renewable electricity	~0–1 (life-cycle, from equipment)	Under 1%
Pink / yellow	Electrolysis with nuclear / grid power	Depends on grid	Tiny

Electrolysis on an average grid is dirtier than grey hydrogen. At the 2025 world average of ~458 g CO₂/kWh (Ember / OWID), 53 kWh/kg works out to ~24 kg CO₂/kg H₂. That is why EU rules for “renewable fuels of non-biological origin” demand additionality plus temporal and geographical correlation with renewable supply.

How electrolysis works

An electrolyser sends direct current through water and splits it: hydrogen forms at the cathode, oxygen at the anode.

2 H₂O + electricity → 2 H₂ + O₂

Theoretical minimum energy = 39.4 kWh/kg H₂ (HHV) | Energy content = 33.3 kWh/kg (LHV) System efficiency (LHV) = 33.3 / specific consumption

Example: 33.3 / 53 kWh/kg ≈ 63% Water: ~9 kg pure water per kg H₂ (10–15 kg raw water incl. treatment)

Technology	Maturity	System consumption (kWh/kg)	Strengths	Weaknesses
Alkaline (AEL)	Mature, cheapest per kW	50–56	Low cost, no precious metals, large stacks	Slower response, lower current density
PEM	Commercial	50–58	Compact, fast-ramping, high-pressure output	Iridium and platinum catalysts
Solid oxide (SOEC)	Early commercial	37–42 (electricity) + heat	Highest electrical efficiency using waste heat	High temperature, degradation, cost
AEM	Pilot / early	50–55	Low-cost materials with PEM-like operation	Durability unproven at scale

Electrolysers are rated in MW of electrical input. A handy rule: 1 MW running around the clock makes about 450 kg of hydrogen per day (24,000 kWh / 53 kWh/kg), or roughly 160 tonnes a year.

The efficiency chain

Every conversion loses energy. Here is what is left from 100 kWh of renewable electricity:

Pathway	Steps	Useful energy delivered
Battery EV	Grid → charger → battery → motor	70–80 kWh at the wheels
Hydrogen fuel cell car	Electrolysis → compression → transport → fuel cell → motor	25–35 kWh at the wheels
E-fuel in combustion engine	Electrolysis → CO₂ capture → synthesis → engine	10–20 kWh at the wheels
Heat pump	Grid → heat pump (SPF 3)	250–350 kWh of heat
Hydrogen boiler	Electrolysis → pipeline → boiler	50–60 kWh of heat
Hydrogen storage → power	Electrolysis → storage → turbine/fuel cell	30–45 kWh of electricity

This gap explains the research verdicts. Rosenow (Joule, 2022) went through 32 independent studies and found none that supported hydrogen for widespread home heating. Ueckerdt et al. (Nature Climate Change, 2021) argued that e-fuels should go first to sectors that cannot be electrified.

What does green hydrogen cost?

The levelised cost of hydrogen (LCOH) depends mostly on two things: the price of electricity and how many hours the electrolyser runs.

LCOH (€/kg) = [CAPEX × CRF + fixed O&M] / annual kg + electricity price × kWh/kg + water, stack replacement

CRF (capital recovery factor) = r(1+r)^n / ((1+r)^n − 1)

Worked example: 100 MW electrolyser fed by solar + wind

Installed system cost: €1,800/kW, or €180 million. This covers the full plant with balance of plant, compression and grid connection. The IEA reports installed costs of roughly $2,000–2,600/kW for recent projects outside China, and much lower Chinese equipment prices.
Lifetime 25 years, WACC 7% → CRF = 0.0858; fixed O&M 2.5%/yr → €19.9 million/yr.
Capacity factor 50% (hybrid solar + wind on a good site) → 438,000 MWh/yr → 8,264 t H₂/yr at 53 kWh/kg.
Electricity at €35/MWh → 53 × €0.035 = €1.86/kg.
Capital + O&M: €19.9 m / 8.26 m kg = €2.41/kg. Stack replacements, water and the rest add ~€0.25/kg.
LCOH ≈ €4.50/kg.

Run the same plant on solar alone at a 25% capacity factor and the capital cost per kg doubles to ~€4.80. Even with cheaper electricity, you end up near ~€7/kg. Utilisation decides the outcome. You can test the trade-offs in the green hydrogen calculator and the LCOE calculator.

Scenario	Electricity €/MWh	Capacity factor	Indicative LCOH
Grey hydrogen, gas at €30/MWh	—	—	€1.5–2.5/kg (+ €0.8–1.0 at €80/t CO₂)
Green, northern Europe, offshore wind	60–80	45–55%	€6–9/kg
Green, solar + wind hybrid (Chile, Australia, Middle East)	20–35	45–65%	€3.5–5.5/kg
Green, solar only, sunny site	20–30	22–30%	€5–8/kg
Long-term targets (IRENA, IEA net-zero pathways, 2030–2050)	15–25	50%+	€1.5–3/kg

Hitting the much-quoted “$1/kg” target (US Hydrogen Shot), or even €2–3/kg, needs very cheap electrolysers and very cheap renewables that run many hours a year. In 2023–2025 many announced projects were delayed or cancelled: costs came in higher than planned, and buyers would not pay the premium.

The hydrogen ladder: where it makes sense

Analyst Michael Liebreich popularised a simple ranking of uses by how hard it is to avoid hydrogen:

Strong case (no good alternative):

Ammonia for fertiliser: swapping out grey hydrogen in a 180+ Mt/yr market.
Refineries and existing chemical uses: they already consume hydrogen.
Green steel: iron ore reduced directly with hydrogen instead of coke in blast furnaces. Steel causes roughly 7% of global CO₂ (IEA), and each tonne of DRI steel needs about 50–60 kg of H₂.
Shipping fuels: green ammonia or methanol for long-haul vessels.
Long-duration / seasonal storage: hydrogen kept in salt caverns to back up wind-heavy grids through lulls lasting several weeks.

Contested:

Aviation (via synthetic kerosene), long-haul trucking, high-temperature industrial heat, remote mining.

Weak case (direct electrification wins):

Cars, buses, delivery vans, home heating, low-temperature industrial heat, short-term grid balancing.

Transporting and storing hydrogen

Hydrogen is the lightest molecule. At atmospheric pressure, 1 kg takes up about 11 m³. The main storage options:

Method	Conditions	Energy penalty
Compressed gas	350–700 bar	5–12% of energy content
Liquid hydrogen	−253 °C	25–35%
Ammonia (NH₃)	−33 °C or 10 bar	Conversion + cracking: 15–30%
Salt caverns	60–180 bar underground	Low; geology-dependent
Pipelines	Repurposed gas pipelines	Embrittlement and compressor costs

Moving hydrogen across oceans is expensive, so many analysts expect trade in derivatives (ammonia, methanol, iron) rather than hydrogen itself. Some heavy industry may relocate to where renewables are cheap, an effect known as “renewables pull”.

Policy: how governments are trying to close the cost gap

Green hydrogen costs roughly two to four times as much as grey hydrogen today, so nearly every project depends on public support:

European Union. The Renewable Energy Directive sets binding sub-targets for renewable hydrogen in industry (42% of hydrogen used in industry by 2030) and in transport fuels. The European Hydrogen Bank holds auctions that pay a fixed premium per kilogram produced. In the first round in 2024, seven winning projects totalling about 1.5 GW bid premiums of roughly €0.37–0.48/kg. Carbon pricing under the EU ETS and the carbon border adjustment mechanism (CBAM) for ammonia and steel close more of the gap.
United States. The 45V production tax credit, created in 2022, pays up to $3/kg for the cleanest hydrogen, with strict hourly-matching rules phasing in. A 2025 law restricts the credit to projects that start construction before 2028, which has made the US pipeline less certain.
China holds the majority of global electrolyser manufacturing capacity. It has also commissioned the world’s largest green hydrogen plants, tied to solar and wind in Inner Mongolia, Xinjiang and Ningxia. Chinese alkaline electrolysers sell for a fraction of Western prices.
Exporters. Chile, Australia, Morocco, Namibia, Oman, Saudi Arabia and Egypt want to export green ammonia and other derivatives made with cheap solar and wind.

According to the IEA’s Global Hydrogen Review, announced projects would multiply low-emission hydrogen output by 2030, yet only a small fraction have reached a final investment decision. Technology is not what holds them back. Bankable demand is: buyers willing to sign long-term contracts at a premium.

Safety and climate side effects

Hydrogen burns across a wide range of concentrations (4–75% in air) and ignites with very little energy, but it rises and disperses quickly. It also embrittles some steels. Leaks have a climate cost: hydrogen warms the planet indirectly by extending methane’s lifetime, and recent studies put its 100-year global warming potential at around 11 ± 5. Leak rates have to stay low for the climate benefit to hold.

Bottom line

Green hydrogen is a vital but narrow tool. Production eats a third or more of the input electricity, so it belongs where electrons cannot go directly: fertiliser, steel, shipping fuels, chemicals and seasonal storage. For cars and home heating, batteries and heat pumps are several times more efficient. In the mid-2020s, even the best locations produce it at roughly double the cost of grey hydrogen, and getting costs down depends on cheap renewables keeping electrolysers busy many hours a year. Work through the numbers in the green hydrogen calculator and check where renewable resources are strongest on the world energy map.

Calculators for this topic

Green hydrogen & LCOH Size an electrolyzer (alkaline, PEM or SOEC) and see how many tonnes of hydrogen it makes, how much water and electricity it uses, and what each kilogram costs, including stack replacements and degradation, with a capacity-factor sensitivity chart. LCOE calculator Capex, fixed and variable O&M, fuel and heat rate, capacity factor, lifetime, WACC, construction time, degradation and carbon price → the levelized cost per MWh, broken down by component and compared across 11 technologies. Energy unit converter Convert any amount of energy between joules, watt-hours, calories, BTU, therms, tonnes of oil or coal equivalent, barrels of oil equivalent, electronvolts and foot-pounds. Shows all units at once, with real-world equivalents. Solar panel output & payback Simulates every hour of a full year at your exact location using NASA satellite weather, then turns the energy into savings, payback time and CO₂ avoided. Wind turbine energy & payback Pick a site and a turbine: we download a full year of hourly NASA wind at 50 m, shear it to your hub height, correct for air density and losses, and turn it into kWh, capacity factor, revenue and payback.

Frequently asked questions

What is green hydrogen?

Hydrogen made by splitting water in an electrolyser that runs on renewable electricity, so production emits almost no CO₂. Most hydrogen today is grey: it comes from natural gas without carbon capture and emits roughly 10–12 kg CO₂ per kg of hydrogen.

How much electricity does it take to make 1 kg of hydrogen?

Commercial electrolysis systems use about 50–55 kWh per kg of hydrogen including auxiliaries. The theoretical minimum is about 39.4 kWh (the higher heating value). On a lower-heating-value basis, one kilogram holds 33.3 kWh of energy.

How much does green hydrogen cost?

Most estimates for mid-2020s projects land at roughly 4–8 US dollars per kg. Grey hydrogen costs about 1–3 dollars per kg, depending on gas prices. Electricity cost and how many hours the electrolyser runs matter most.

Is hydrogen good for heating homes?

Generally no. After production, transport and combustion in a boiler, only about 50–60% of the original electricity comes out as heat. A heat pump turns the same electricity into 250–400%. Independent reviews of dozens of studies conclude that heat pumps and district heating are more efficient and cheaper for buildings.

Can hydrogen power cars?

Fuel cell cars exist, but they have lost ground to battery EVs. They need about two to three times as much electricity per kilometre, and refuelling stations are scarce and expensive. Hydrogen may keep a niche in some heavy, long-distance transport, though battery trucks are improving fast.

What are the best uses for green hydrogen?

Replacing grey hydrogen where it is already used, such as ammonia fertiliser production and oil refining. Beyond that: green steel made by direct reduction of iron ore, methanol and ammonia as shipping fuels, and possibly long-duration seasonal energy storage.

Sources & references

Figures in this guide are typical ranges drawn from the sources above; your own numbers depend on location, prices and equipment. Use the linked calculators for site-specific estimates.