Universita di Ferrara, Dipartimento di Fisica, Via Saragat 1, 44100 Ferrara, Italy. *Phone: +39 0471 055337; Fax: +39 0471 055339; E-mail: maurizio.armani@eurac.edu ABSTRACT: This paper presents monitoring data and performance results of 12 photovoltaic systems installed in South Tyrol, which are based on different technologies, mainly crystalline and CdTe modules, and various dimension, from few kWp to more than 800 kWp. The target of the monitoring is an evaluation of performance ratio of the different systems, under the real regional climatic condition, for the benefit of installers and final users, and the collection of data to allow a better understanding of loss mechanisms. This paper summarizes 18 months of monitoring results. The monitored data include current from the PV array, array voltage, AC power delivered, global horizontal irradiance and ambient temperature, obtained from 26 weather station scattered on the region, and array temperature. The purpose of this work is to compare and to present operational performance results of grid-connected PV systems, as collected and elaborated for the project CoPES; a cooperation project between applied research institutions and several SMEs. The obtained results were used mainly as a feedback for the industry concerned with installation; besides that, selected results were used as a reference parameter for the validation of a new code for the efficiency prediction modeling of a PV module operating in outdoor conditions. Keywords: system performance, monitoring, simulation 1 INTRODUCTION The aim of the activities conducted under the project CoPES [1] was to be the basis for the development, in South Tyrol, of a pole/centre for the know-how transfer in photovoltaics, allowing local companies to acquire strong positions as actors in PV market in Italy. Research activities were carried out using tools such simulation and monitoring of certain facilities installed during the development of the project. Monitoring activities and simulation carried out had not only the aim to deepen knowledge about the processes of generation from photovoltaic source, but also to transfer information to designers and installers with repercussions on the market, improving the quality of design, margins of economic return, compared with a greater accuracy in forecasting yield and, more generally, increasing the appeal shown by the sector. This need occurs as a result of issues relating to estimates of return linked to the difference between the operating conditions set as standard conditions (STC) and those relating to the losses attributable to real outdoor operating conditions. In this paper the simulation results from different selected software packages are compared with the results obtained from the monitoring campaign, which at its end counts 1935.37 kWp monitored, equivalent to 24.11% of total power installed in the Province at the time of conclusion of this project, the means by which the data were collected. 2 MONITORING The selected plants shown in Table I are characterized by different technologies, distributed in the southtyrolean territory, equipped with automatic, commercial, data acquisition systems supplied by the producers of the inverters. The monitored plants exploit a service of remote monitoring based on measurements taken by the same inverter (embedded monitoring), summarized in some cases from measurements taken directly from sensors on considered sites, such as temperature of the modules and radiation in the plane of the modules, or using information derived from the provincial weather stations scattered around South Tyrol.