The article presents the main design features and photovoltaic requirements of a FPCS (floating photovoltaic cover system) for water irrigation reservoirs whose purpose is to reduce the evaporation of water while generating electrical power. Also, a summary of installation costs and relationship with the yield performance is deeply analyzed. A prototype of 20 kWp was implemented, and given the success of the results observed, the whole surface reservoir was covered (4490 m(2) and 300 kWp). The paper analyses the first electricity productions of the system and from these data the CO2 balance of the facility is calculated. (C) 2014 Elsevier Ltd. All rights reserved.