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The paper describes the performance of the grid-connected 1-kW PV system installed on a grammar school in Poland after eight years of operation. It was designed and installed in year 2000 and from year 2001 it is fully monitored according to guidelines of standard IEC 61724. System was build from 20 a-Si modules (Millennia MST 50 MV by BP Solar) and Sunny Boy inverter. Monitoring system consists of set of meteorological and electrical sensors connected to Sunny Boy Plus Controller supported by PC computer. During eight years of operation, system has produced 4430 kWh of energy. Due to the process of stabilization of electrical parameters of amorphous silicon modules, in first three years of system work, PR values are decreasing. After the end of that process PR is in range from 0.52 to 0.6. Analyzing that value one must remember that due to damage of two modules in second year of system work, its actual nominal power is lower (900 W) that the one that was considered during the calculations (1000 W). Everything that has been written about PR also applies to System Efficiency. Its value is about 3.5%. The inverter efficiency is about 92%. Data gathered by the monitoring system also enabled to perform wide range of analysis of the influence of meteorological parameters, such as irradiance on both horizontal and module plane or temperature, on the system parameters, such as System and PV Generator Losses, System and Inverter Efficiencies, Performance Ratio, or system output electrical parameters, such as DC and AC output power and output DC voltage. The analysis includes also measurement by portable l-V curve tester and infrared camera.