This study aims to evaluate the technical specifications and maximum capacity of an on-grid Solar Power Plant (PLTS) system at the 150 kV Muara Rupit Substation in South Sumatra. The research employs a technical feasibility study approach using PVsyst version 8.0.6, simulating three PLTS scenarios based on Longi LR5-72HTH-595M modules rated at 595 Wp. Each scenario varies by inverter type, namely a 2200 kWac central inverter, 11 units of 172 kWac string inverters, and 18 units of 100 kWac string inverters. All configurations are designed to optimize the use of 9,881 m² of effective land area. Simulation results show that the maximum installable capacity is 2,276 kWp using 3,825 solar modules. The configuration with 172 kWac string inverters yielded the best performance, with a performance ratio of 86.21% and annual energy output of 3,535.6 MWh. This study concludes that inverter configuration plays a significant role in system efficiency and should be a key consideration in medium-scale PLTS design.