I was only commenting on electrolysis, I did not make any statement about hydrogen power in general. However, now that you brought it up, the other issues that

I was only commenting on electrolysis, I did not make any statement about hydrogen power in general. However, now that you brought it up, the other issues that you mention are very surmountable: - Transport. You can either transport hydrogen via pipelines or simply produce it via electrolysis in-place. You have to get the electricity to the destination somehow, so this doesn't really differ between electric and hydrogen cars. - Building up pressure. Energy required to build up pressure is related to how much the volume is reduced (force x distance and all that...) Conveniently water is almost incompressible, so you can raise the water to the desired pressure cheaply before you electrolyse it. https://en.wikipedia.org/wiki/High-pressure_electrolysis https://en.wikipedia.org/wiki/High-pressure_electrolysis says this can be done at 97% efficiency.