In 2005, Sacramento Municipal Utility District (SMUD) increased the number of grid-connected PV systems to approximately 1050 leading to an installed capacity of over 10 MWac. As the only independent accredited design qualification laboratory in the United States, the Photovoltaic Testing Laboratory at Arizona State University (ASU-PTL) provides an independent performance data to SMUD verifying manufacturers' data. In addition to obtaining the initial performance data, this SMUD-ASU program conducts several reliability and durability evaluations through long-term outdoor testing and accelerated indoor testing. This reliability evaluation program provides information on the predicted performance degradation per year, expected seasonal performance fluctuation and susceptibility to known failure mechanisms. This paper presents and analyzes the results of outdoor tests conducted on 44 modules of three different PV technologies (mono-Si, poly-Si and a-Si) from eight different manufacturers over the exposure period of two to seven years.