Love that kind of urinal, but I don't think they're the best at water usage, because you don't see them often anymore.
Surprisingly, they do meet the "low flow" water usage category, although waterless urinals seem to be the preferred standard now. They are still made by
Kohler,
American Standard, and others, but are usually not stocked and are special order due to low demand. There are two reasons why they are rarely used today:
1. Although they may meet the federal ADA (Americans with Disabilities Act) requirements, they do not meet the handicap access requirements of many states and cities. For example, in California the "basin" of the urinal must protrude a certain minimum distance from the wall, at a certain height, with empty space under it. This requirement can only be met by a wall-hung urinal. (Sadly, the beloved piss trough at my favorite bar was also deemed non-compliant, and had to be replaced to get approval for a renovation.)
2. In ground-floor use in buildings with slab construction (i.e. no basement below), complex plumbing has to be buried in the earth far below the slab, because the drains of these are below the floor level. By contrast, the drain piping for wall-hung urinals is above the floor, behind the wall, making installation, and more importantly repairs, much easier and cheaper. This is also an advantage in the construction and tenant fit-up of multi-story, multi-tenant commercial buildings. (Note that some commercial toilets flush out the back, not down through the base, for exactly the same reason.)
But from a practicality point of view, the old floor urinals are actually much better, and do not have the same issues with piss all over the floor and wall that modern urinals have.