The performance of a PV system can be characterised by the Performance Ratio. The performance ratio can be measured by means of global monitoring and is based on only a few measured variables. The meaning of this indicator is limited to a global impression of the performance, as there is no way to identify improperly functioning components. This paper describes a method to characterise the performance of the PV system in more detail. It is based on analytical monitoring and makes distinction between different types of losses. Low irradiance losses, resistance losses, inverter losses, shading losses and temperature losses etc. can be determined with suitable software. Lost energy due to improperly functioning components can be charted in an easy way. Keywords: Performance - 1: monitoring - 2: evaluation - 3 1. INTRODUCTION The performance of a grid connected PV system can be characterised by a single number, the performance ratio, PR. The performance ratio of a PV system duri...