Compressing the hydrogen to 880 bar to fill a 700 bar tank and then dealing with the thermal changes costs 3-5 kWh per kilogram of hydrogen.

A kilogram of hydrogen has 33.33 kWh of heat energy. Calling it 10% of heat energy is about right.

But fuel cells in vehicles run at about 50% efficiency. So compression actually requires 20% of the energy of they hydrogen.

You don't ship hydrogen compressed to those levels, so there are additional compression costs on pipelines if those are used. Or there are liquification costs for shipment, which are about 11 kWh per kilogram, or a third.

Start with 100 kWh. Throw away 30% for manufacturing it.

70 kWh. Throw away a third for liquifying it.

23 kWh. Throw away 20% to compress it.

19 kWh. Throw away 50% turning it into forward motion.

9 kWh.

Or you could put the electrons in an HVDC cable and deliver 90% of them to a battery charging station and then put them in a battery that's 90% efficient at delivering electricity to forward motion.

80 kWh.

Looks great, doesn't it? Really sensible?

Oh, and try not to get in a significant collision with a 700 bar pressurized tank under your feet. Leaks will be fine outdoors (but not indoors so don't park in your garage), but catastrophic failures would release all that pressure in unpredictable directions at great speed. Think of it as a giant bomb going off under your butt, one that, if you're lucky, doesn't then turn into an air fuel bomb.

It's only the homeopathic numbers of these things on the roads that has prevented a really gnarly outcome.