"These electrolysers currently...consume a lot of energy and water – it can take about nine litres to make one kilogram of hydrogen." OK, I'm an engineer not a

"These electrolysers currently...consume a lot of energy and water – it can take about nine litres to make one kilogram of hydrogen." OK, I'm an engineer not a chemist, but based on the relative atomic weights of water (18) and H2 (2) isn't that the most you would theoretically expect to get?