Water Intensity of Hydrogen
Water intensity is how much water it takes to produce 1 kg hydrogen; electrolysis needs about 9 litres per kilogram for the reaction, and several times more once cooling is included.
In plain terms
Water enters a hydrogen plant for three jobs, and each gives a different number.
- Stoichiometric water is what the reaction splits. One kilogram of hydrogen needs about 9 kg of water by molar mass. The US DOE gives 2.36 gallons (about 8.9 L) per kilogram.
- Process water adds what the water treatment train rejects as brine.
- Cooling water removes the heat from stack losses. With evaporative cooling, this is usually the largest share.
Withdrawal is everything taken from the source. Consumption is what does not return, mostly evaporation and water turned into hydrogen.
Typical range
| Basis | Alkaline | PEM | Source |
|---|---|---|---|
| Process water | ≈11 L/kg | ≈9.2 L/kg | UK DESNZ, 2024 |
| Evaporative cooling | ≈31 L/kg | ≈43 L/kg | UK DESNZ, 2024 |
| Once-through cooling, withdrawal | >1,200 L/kg | >1,800 L/kg | UK DESNZ, 2024 |
For PEM, the US DOE estimates direct consumption at about 30 L/kg (8 gal) with cooling towers and about 9 L/kg (2.4 gal) with dry cooling.
Why it moves LCOH
Water is a small share of LCOH where fresh water is available. At coastal, water-stressed sites such as southern Morocco, it means desalination, intake works and brine disposal. These add CAPEX and electricity, and permitting risk. Cooling choice is the biggest lever: dry cooling cuts water use but costs more and uses more fan power.
Common mistake
Related terms
Sources
- Hydrogen Program Record 25003: Water Use for Hydrogen Production, U.S. Department of Energy, Hydrogen Program, 2025
- Water Demand for Hydrogen Production (v2.0), Ricardo, UKCEH and BGS for the UK Department for Energy Security and Net Zero, 2024
- Water for Hydrogen Production, IRENA and Bluerisk, 2023