The goal of the following work is the correct re-design of a medium scale photovoltaic plant, in order to increase its energetic and, consequently, economic performances (revamping); an existent 1 MW grid-connected plant located in Racconigi (TO), of ground mounted type, will be considered the case study for the revamping operation to which making reference for the whole treatment. After a brief overview on PV technology, the case study plant will be described in its original configuration. Plant’s productivity concept will be defined, and some methods of estimation will be applied in order to determine its value before and after the intervention, so as to estimate the potential energy gain of the revamping operation.