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PV systems that are normally operated under outdoor conditions rarely generate the expected rated power, but instead lose power due to environmental and systematic factors. The most significant environmental performance loss factors are the temperature, angle of incidence, low light conditions, spectrum and soiling whilst degradation, mismatch and conversion losses include some of the main systematic sources of loss. This paper presents the analysis of the main performance loss sources focusing on different technologies installed at the testing facility of the University of Cyprus since 2006. The performed investigation was based on analytical monitoring and evaluation of climatic and system operational data while corrections where applied using manufacturer datasheet parameters. As shown by the results the temperature was the main source of loss in high irradiance countries predominately for mono- and multi-crystalline technologies. The performance losses on annual energy DC yield due to the temperature were found to be in the range 5 % 8 %. Thin-film technologies of amorphous silicon suffer less from temperature rises but demonstrate high initial degradation. The evaluated losses were then used to provide an estimate of the AC Performance Ratio (PR) which was compared against the real AC PR of each technology over the first year of evaluation. The variation between the two parameters was -2.2%-2.5%.