Originally Posted by RustyJC
The reason we can't fuel a fuel cell vehicle with water is that it takes more energy to break the water molecule apart by electrolysis into 2H2 + O2 than is gained by combining 2H2 + O2 into 2H2O (which is what a hydrogen fuel cell does).
Rusty, you nailed it again. There is no free ride.
(waiting for the "BIG OIL AND GOVERNMENT IS SUPRESSING THE MARKET" conspiracy theorists to weigh in)