According to this article, Germany can quickly and affordably convert to a hydrogen based fuel economy.
It projects 400 GW of PV and 280 GW of wind power. Germany had only 60.8 GW of wind in 2019, so this scheme would require over a 4.5x expansion of wind alone... and there is already political pushback about siting. Not to mention multiplying the "environmental fee" which pays for all of this by a similar amount. Stuff to convert electricity to hydrogen, storage systems, and everything else are on top of that. Definitely not cheap, by a long shot.