This paper analyzes a possibility of upgrading hydroelectric plant (HEP) with solar photovoltaic (PV) generator. The main objective of this solution is maximization of green energy production in accordance with local and existing HEP framework. The example of HEP Zavrelje/Dubrovnik in Croatia was used as a paradigm of such exploitation of RES. The results of the analysis confirm that the proposed solution of hybrid work PV-HEP system is natural, realistic, and very promising. By hybridization of these two main natural energy sources, the characteristics of both energy sources are enhanced. The application of such hybrid systems would increase the share of green energy in the electric power systems and thus reduce the CO2 emission from energy sources.