How this green hydrogen calculator works
Green hydrogen is made by splitting water with renewable electricity in an electrolyzer. The physics doesn’t change: every kilogram needs at least 39.4 kWh. The cost does. It hangs on the electrolyzer’s efficiency and price, the hours it runs each year and what the electricity costs. The calculator lays these out side by side:
- Production. Electrolyzer power × hours of operation (from the capacity factor of your power supply) ÷ specific energy use gives kilograms per year. Stack degradation pushes energy use up over each stack’s life, so the calculator applies the average.
- Resources. Water consumption, oxygen by-product and, for SOEC, steam.
- Levelized cost (LCOH). Capital is annualised with the capital recovery factor at your WACC. Stack replacements are discounted to today and annualised too. Fixed O&M, electricity, compression, water and heat are added, and the total is divided by annual production.
- Sensitivity. A chart of LCOH against capacity factor at three electricity prices. It shows the trade-off between cheap intermittent power and expensive firm power more clearly than any table.
The formulas
Worked example: 10 MW alkaline on a wind–solar PPA
The defaults model a 10 MW alkaline electrolyzer (52 kWh/kg when new) fed by a hybrid solar-plus-wind supply with a 55% capacity factor at €45/MWh:
- it runs about 4,820 full-load hours, using 48 GWh of electricity;
- with 0.12%/1,000 h degradation, average consumption over a stack life is about 54.5 kWh/kg (61% LHV efficiency), for about 880 tonnes of hydrogen a year, or 2.4 t per day;
- it needs about 13,000 m³ of water and releases 7,000 t of oxygen;
- capex at €1,600/kW is €16 million, with one stack replacement after about 16–17 years;
- LCOH ≈ €4.5/kg: electricity €2.45, capital €1.55, O&M €0.36, stack replacement €0.12 and water €0.03 per kg.
Sold at €6/kg, the hydrogen gives the project a positive NPV of about €15 million. Switch to the 1 MW PEM on solar preset and LCOH jumps above €10/kg: small scale, higher capex and a 22% capacity factor all push it up. The 2030 target preset (€700/kW, €25/MWh) shows the route to roughly €2/kg that policymakers are aiming for.
How to read the results
- Hydrogen production: annual tonnes, the daily average and hourly output at full load.
- LCOH: compare it with grey hydrogen (about 1–3 per kg), subsidy auction prices or the value of the fuel you replace. The per-MWh (LHV) figure lets you set it against natural gas.
- LCOH breakdown: if electricity dominates, work on efficiency and power price. If capital dominates, raise utilisation.
- Sensitivity chart: each curve falls steeply at low capacity factors and flattens above 50–60%. The best point balances cheaper intermittent electricity against capital sitting idle.
Typical values
| Technology | System energy use | Efficiency (LHV) | Stack life | Installed capex (2023–24) |
|---|---|---|---|---|
| Alkaline (AEL) | 50–55 kWh/kg | 61–67% | 60,000–90,000 h | 1,400–2,000 per kW |
| PEM | 52–58 kWh/kg | 57–64% | 50,000–80,000 h | 1,700–2,500 per kW |
| SOEC | 37–42 kWh/kg + heat | ~75–85% incl. heat | 20,000–40,000 h | 2,500–4,000+ per kW |
| AEM | 50–57 kWh/kg | 58–66% | < 30,000 h | early market |
Useful conversions: 1 kg H₂ = 33.3 kWh (LHV) = 39.4 kWh (HHV) ≈ 11.1 Nm³; a fuel-cell car uses about 0.8–1 kg per 100 km; one tonne of hydrogen makes about 5.7 t of ammonia.
Tips to lower LCOH
- Raise utilisation. Combining wind and solar, or adding a small grid top-up, often lowers LCOH even at a higher average power price.
- Oversize the renewables relative to the electrolyzer so it spends more hours at full load.
- Sell the by-products. Oxygen or recovered low-temperature heat can trim costs by several percent.
- Watch stack life and degradation. A longer-lived stack can save you an expensive mid-life replacement.
- Count compression and storage. Delivery at 350–700 bar or as a liquid adds 2–12 kWh/kg (enter it in the compression field), plus the cost of storage.
- Model the power supply itself with the wind farm calculator or solar panel calculator.
Limitations
The model assumes a flat capacity factor and a constant electricity price. Real renewable supply fluctuates, and minimum-load limits, ramping, hydrogen storage and offtake constraints all cut effective utilisation. Taxes, grid fees, land, financing structure, transport and subsidies are excluded. Capex figures move fast and differ a lot between suppliers and regions, so check recent sources such as the IEA Global Hydrogen Review before you rely on any single number.
Method & assumptions
Hydrogen (kg/yr) = MW × 8,760 × CF × 1,000 ÷ specific energy use (kWh/kg). The specific use rises with stack degradation (%/1,000 h) and resets at each replacement, so the average over a stack life is applied. Efficiency (LHV) = 33.33 ÷ kWh/kg. Water = kg × L/kg; oxygen ≈ 7.94 kg per kg H₂. LCOH = annualised capex (CRF at your WACC) + annualised present value of stack replacements + fixed O&M + electricity + compression + water (+ steam for SOEC), divided by annual kg.
Frequently asked questions
How much electricity does it take to make 1 kg of hydrogen?
How much water is needed to produce hydrogen?
What is the cost of green hydrogen?
How much hydrogen does a 1 MW electrolyzer produce?
What is LCOH?
Which is better, PEM or alkaline electrolysis?
Why does capacity factor matter so much?
Sources & references
- IEA — Global Hydrogen Review 2024
- IRENA (2020). Green Hydrogen Cost Reduction: Scaling up Electrolysers to Meet the 1.5 °C Climate Goal
- Clean Hydrogen Partnership — Strategic Research and Innovation Agenda (electrolyser KPIs)
- US DOE Hydrogen and Fuel Cell Technologies Office — Hydrogen production via electrolysis
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