The instruction manual requires you to have some clearance around this unit for ventilation and recommends 10 cm on all sides.
The way this mounts is you screw a bracket to the wall then you hang the inverter on the bracket. Because of that you need a small clearance to lift it over the bracket. On my demo system I wanted it as close as possible to the ceiling and it ended up when installed about 1/2" clearance. See our short video in the "additional information" tab.