Thin film amorphous silicon based PV systems are a rather new and promising photovoltaic technology with plenty field for technological development and potential for unique applications such as integration within the built environment. Nevertheless, in order for the technology to be established, further technical development is required and economical aspects should be tackled, both in the module and system level. From a commercial point of view, the ultimate goal of a PV system, once installed, is to cost effectively deliver the highest possible energy yield. In reality, the actual energy yield every system delivers is lower than the theoretical rated performance. Location and environmental factors, such as heating of the modules, irradiance, dirt accumulation, angle of incidence, Etc. affect the performance of the systems. Understanding the behavior of this new technology under real operation conditions can provide reliable insights for its further development, help better estimate the energy yield amorphous silicon systems can provide and perhaps, help the technology differentiate itself from the better commercially established crystalline silicone based one. This work investigates the effect of most of the location and environmental factors affecting the performance and the ultimate energy yield of a photovoltaic system comprised of flexible and lightweight amorphous silicon modules. The factors responsible for this performance decrease are individually investigated, and its effects are quantified by addressing in which manner they decrease the performance ratio of the system. A performance monitoring system was built expressly for this purpose, which data acquisition plan was based on the IEC 61724 -1 (2017) standard. A computer model with the capability of simulate the performance of the system after correcting for the evaluated mechanism was also constructed as part of this work using Matlab. This model was based on an experimental characterization of the modules, using live performance data as an input to give a performance ratio, and an assessment of the effect of loss factors. The results allocated the source of the system losses up to a 78% of the total power decrease, considering the rest of the unexplained observed losses as effects of the active material degradation. The performance ratio of the system was reported on a daily bases for the full evaluated period, concluding a strong correlation between a high irradiance and a high performance ratio. The common literature claim of a better behavior of thin film a-Si:H technologies compared to c-Si was verified under this study, and the effects of system operation under low irradiance conditions was identified as the dominant loss mechanism.