> The bus gets lighter and more efficient as it uses fuel.
This argument is weak. To get any kind of reasonable energy density you have to compress hydrogen to 10,000psi. The tanks to contain a gas at that pressure are heavy enough that the weight of gas inside is almost negligible. Especially in ground vehicles which aren't hugely sensitive to weight.
I think the relevant numbers here (to evaluate the statement "The bus gets lighter and more efficient as it uses fuel.") would be the total weight when empty vs when full.
The tank weighs at least 10x what the hydrogen weighs, so yes it’s relatively little per trip, but it does add up over the lifetime of the vehicle and I thought it was worth mentioning. Same goes for very high voltage in BEVs. There’s weight savings to be had by maximizing voltage which allows you to reduce the thickness of the wiring. But the savings are small compared to the weight of the battery.
This argument is weak. To get any kind of reasonable energy density you have to compress hydrogen to 10,000psi. The tanks to contain a gas at that pressure are heavy enough that the weight of gas inside is almost negligible. Especially in ground vehicles which aren't hugely sensitive to weight.