[jsjohnst]

Gasoline powered internal combustion engines average around 20% efficiency, cutting edge new stuff still doesn’t really break 40%. Need to keep that in mind! Yes, gasoline itself is very energy dense, but that doesn’t mean we efficiently use it in automobiles.

[Gibbon1]

Amusingly lithium is also really energy dense too. The difficulty is it's only 2-3% of the battery by weight. Upside of that is there is a lot of room for improvement. Not that it's easy low hanging fruit though.

For transport hydrogen suffers a lot of the same issues as lithium. The storage systems are all heavy. Compare with an empty gasoline tank you can lift with one hand.

[Symmetry]

In terms of energy efficiency in powering moving vehicles then yes, hydrogen is as energy efficient as anything else. That's why I complained about it's energy density rather than its efficiency in that context. In terms of grid storage batteries are ~99% efficient and pump storage is 75% efficient.