Second Law of Thermodynamics: "You can't break even"re: Making hydrogen (and oxygen) from water and surplus electricity,
yes BUT it requires MORE energy to break down H2O into H and O than you can get from using the H and O....
one of those nasty Physics laws.....
That's a drawback of ANY form of unstable energy generation: in order to keep the supply stable, you need to generate more than is needed whenever possible, and store it - and in ALL cases, you will never get back as much as you put in. The only differences between various storage media is how much you can get back, and how long you can store it.