Compact apparatus (10) for the semi-automatic horizontal assembly of photovoltaic panels (200) with solar cells (112), made up of a multi-function workstation in the form of a pilot system integrating multiple working and conveying means which carry out the various operations concomitantly and in a coordinated way. On the sides of the working surface (100) there is the loading zone of the cells, the loading zone of the conductive ribbons and a pair of longitudinal rails which are intended to guide two mobile gantries (120, 130), which roto-translate above the working surface, from one loading zone to the other, being equipped for the purpose of assembly. In particular, said compact apparatus (10) is versatile in use and allows to obtain already in the experimental laboratory phases the levels of accuracy and control of an industrial system, for the purpose of optimizing the product and the assembly technologies reducing wastes and faults.