This chapter presents the performance of a 20 MWp grid-connected PV system installed in a harsh environment, Adrar in the South of Algeria. The results were monitored over a period of 1 year, from January 2018 to December 2018. The PV system assessment includes final and reference yields, system efficiency, performance ratio, capacity factor, and total system losses. The total yearly energy delivered to the grid was 35892.22 MWh, and the monthly average reference and final yields of the system are in the range 5.92–8.1 (h/day) and 4.39–5.56 (h/day), respectively. Furthermore, the annual average daily PV system efficiency, performance ratio, capacity factor, and total losses were 10.82%, 71.71%, 20.76%, and 2.04 h/day, respectively.