"Heck, why not just store the hydrogen part, and burn it in an oxygen atmosphere when you want water?"

Reminds me of a chemistry class way back in high school.

We had seperated water into hydrogen and oxygen using electricity and had the gasses stored in those round glass things with long snouts (forgot the name of that glassware). Someone asked the teacher, "Can you turn it back into water again?"

He said "Sure!" and whipped out his lighter. Next thing he said, as he was rising from the floor behind his desk, was "Am I cut?! Am I cut?!" We never found the resulting water. Just glass fragments all over the place. (Nobody was hurt, luckily!)