Today's environmental policies are largely devoted to fostering the development and implementation in Europe of renewable energy technologies, such as grid-connected photovoltaic solar energy, which are being actively promoted by European Union countries. This article describes an environmental decision-support system (EDSS) for selecting optimal sites for grid-connected photovoltaic power plants. This system combines multicriteria analysis and the analytic hierarchy process with geographical information systems (GIS) technology and at the same time takes into account environment, orography, location, and climate factors.