can this be mounted on the wall?

It can be mounted on a wall, but the lamp cover will fall out, because it does not fit in the fixture well enough to allow such a mounting position.

Yes, it will work. However, we have not tested ceiling fixtures installed on the wall. All GEL fixtures meet current UL testing and standards if they are mounted as per our manufacturers instructions. Ceiling mounting the fixture will be covered under the warranty limits, as posted in the instructions. Wall mounting is not. Customers who choose to do so are responsible for securing the fixture to the electrical box and wall with extra fasteners if needed. IMPORTANT: Note that mounting the fixture on its side may create uneven heat ventilation. In the top half of the fixture the air, bulb and ballast will have a higher temperature. In other words, wall mounting the fixture may cause a shorter life expectancy on the bulb and ballast.