RE: 20 cubic metres of water per ton of hydrogen28 Oct 2025 13:48
I was speaking with Justin about this. He kindly provided the info below.
Considering the atomic properties of water, HโO, and the fact that oxygen is 16 times heavier than hydrogen, oxygen accounts for 89% of the water's mass. This means that the theoretical amount of water required to produce 1kg of hydrogen is ~9 litres (8.92 to be precise). Our electrolyser systems incorporate a water management system that performs several functions. These include cleaning incoming water, circulating clean water through the stacks, polishing recirculating water, and repatriating water captured from the product hydrogen stream.
Water is circulated through the stacks at a high rate, ensuring effective removal of product oxygen and heat. Much less than 1% of the water circulated through a stack is consumed in electrolysis.
There was a study in 2020 from Hydrogen Europe, which stated:
Based on the atomic properties of water, 1 kg of hydrogen requires 8.92 litres of water. If the 10 million tons (MT) hydrogen production target of the EUโs Hydrogen Strategy is reached by 2030, 89 million tons of water would be used by electrolysis. This would represent 0.00478% of all annual freshwater resources of the EU, 0.0432% of all annual French freshwater resources and 0.0288% of all annual precipitation (i.e. rainfall) in the EU27.
In addition, Hydrogen Europe also stated in the report, that if you compare water consumption for electrolysis with other energy processes, you would find that crude oil recovery and diesel refining uses about 40% more water that the production of green hydrogen per unit of energy.
Regarding PEM vs Alkaline, it is not so much a difference in water use as the fact that the hydrogen produced from a PEM system is purer because it does not use an electrolyte such as KOH. The oxygen produced is currently vented. It is not medical-grade, but it could be used in areas such as fish farming, where water needs to be oxygenated.