Renewable energy sources have received an increasing attention during the last years. Solar radiation is one of the most accessible energy resources and photo-voltaic conversion is a relatively easy and cost-effective solution. The major drawback of solar radiation and photo-voltaic conversion is the low energy density and the low conversion efficiency, that can be reduced to unacceptable levels by several factors, including pollution and dust deposit on the panels. Therefore, it is extremely important to monitor the production of every photo-voltaic generation plant and compare it with the incident solar radiation, in order to schedule maintenance at the optimal time to keep the overall generation efficiency at an acceptable level. This paper proposes and discusses a remote monitoring system for on-line tracking of the energy performance of a photo-voltaic generation plant. Some experimental results on a lab prototype are discussed.