For many years, amorphous silicon photovoltaic modules have had difficulties to establish themselves in the grid-connected PV-market. Causes for this lack of market acceptance of first generation amorphous silicon PV modules were their relatively low conversion efficiencies, unstable power and not well understood outdoor characteristics. Various manu-facturers of amorphous silicon modules have resolved these initial problems by enhancing the efficiencies of their cells, while at the same time improving the long-term stability of the products. Still, the outdoor behaviour of amorphous silicon modules is not well understood by many users, even by insiders of the PV-community. Results of this study will show that new generation multi-junction amorphous silicon modules, and in particular UNI-SOLAR ® modules based on the Triple Junc-tion solar cells, perform excellent under western European climatic conditions, with yields and performance ratios signifi-cantly higher than all present crystalline silicon technologies. This effect is especially pronounced under low light conditions and under non-ideal orientations. The enhanced outdoor performance, up to 20 % higher on a yearly kWh/kWp base, can be attributed to the higher sensitivity for low light conditions and for diffuse light, better performance at high temperatures and improved shadow tolerance of UNI-SOLAR ® modules.