Same place everyone seems to think the electricity will come from for all the battery manufacturing plants, and for all the battery powered cars.

There are many ways to get the hydrogen necessary with no methods exceeding the challenges already faced in bringing oil to the pumps. And there are future methods around the corner that will become more efficient, such as using photosynthesis.

As for the power issue on either side, it's a step forward to eliminate the pollution from billions of tiny internal combustion engines, and concentrate the problem to thousands of power generation centers. The energy problems can't be solved overnight, but steps can be taken to continue our independence from oil based solutions. Tossing out an idea just because it's going to require a coal plant here or there is simply refusing to address the problem now, and once again going back to the "well, someone in the future will figure it out" mentality.