Solar-powered photovoltaic (PV) system encounters a significant amount of losses due to different derating factors of PV modules throughout its lifespan. Thus, proper investigation is much needed to grasp the technical and economic impact of derating factors on the solar PV system, specially the one which is connected to the utility grid. This study performs a comprehensive discussion on various PV loss parameters followed by a techno-economic-environmental assessment of combined derating factor on an grid-connected and optimally tilted PV system located at Hatiya, Bangladesh using HOMER (Hybrid Optimization Model for Multiple Energy Resources) software. Some criteria linked with derating factor such as PV degradation and ambient temperature are further explored to analyze their impact on the aforementioned power system. Simulation results show that the system provides the best technical performance concerning annual PV production, power trade with grid, and renewable fraction with less emissions at a higher value of derating factor since it represents the lower impact of loss parameters. Similarly, financial performance in terms of net present cost (NPC), levelized cost of energy (LCOE), and grid power exchange cost is found lower when derating factor value is higher.