Thought just occured to me.

In order to run on H2O it has to be distilled water.

Also there's the question of what the effect of huge amounts of O2 would be on the atmosphere, too.

Because 02 would be the by product of breaking down those molecules would it not?

200,000,000 vehicles spewing flammable o2 into the atmosphere?

Sounds like that's a problem waiting to manifest to me.

The solution is STILL solar, folks.