I think the point is that it can use that small amount of energy to break the hydrogen bond in the water, releasing more energy than was used.
Edit: Apparently I made a mistake. See the correction, which I was the first to upvote.
Edit: Apparently I made a mistake. See the correction, which I was the first to upvote.
The device appears to use water->hydrogen as an energy storage mechanism, to solve (at some efficiency cost) the issue of energy demand generally being out of sync with the supply from the sun. You put energy in to convert water into hydrogen+oxygen, and then you can get that energy back out by converting it back into water.
In the case of water, 2 H20 -> 2 H2 + O2 is endothermic, but reactions do not have to be endothermic, or else chemistry would be very boring and cold.
Well, that's an interesting UI idea...