For fixed installations, piped in, nothing.
For vehicles, hydrogen has a very low energy density giving low range. Larger fuel tanks compensate somewhat but they take up space that could otherwise be used for cargo. This was discussed in depth, including comparisons of energy density for different fuels, some time ago on this board, including references.
If you convert the hydrogen to another fuel or adsorb it on something to improve its energy density (lots of people working on this), hydrogen looks a lot better as a mobile fuel.
Henning had the idea that a scuba tank of gaseous hydrogen had enough energy to power a home by combustion, and that was the point of my comment.