[Christ]

The tank has a water volume of 87 liters and is rated up to 3,600 psi. At 3,600 psi, the tank holds 590 SCF of hydrogen, which is equivalent to 1.4 gallons of gasoline. At 200 HP, this tank is emptied in about 5 minutes.


^^^ quoted from the link that orange4boy provided.

1.4 gallons of gasoline used to create 200 HP for 5 minutes equates to 15 gallons of gasoline necessary to make 200HP for an hour, or .075 gallons per HP/Hr. (the figure that really matters for efficiency of an engine) At 6 lbs per gallon, that figure breaks down to .012lbs per HP hour.

So it would take 590 cuft of hydrogen (which is equivalent to 1.4 gallons of fuel (energy equivalent) to create that same figure of .075 gallons per hour, at a cost of ~ 21 cents per cubic foot (2007 average), or a total volume cost of $123.90, compared to 1.4 gallons of liquid gasoline at approx $4.

That's what? Like 300 times the cost for the same output.

A K tank costs about $40 to fill, and contains about 1 pound of hydrogen.