Floating photovoltaic solar plants urge in a time when increasing demand for energy requires a shift to renewable energy resources as the limited availability of fossil fuels as well as global warming and climate change are all a reality. Furthermore, the increasing cost of land acquisition due to growing worldwide population and, consequently, reduced available land area restricts some countries such as Japan to construct big solar farms, giving room for the opportunity to deploy floating solar photovoltaic systems in water reservoirs. This research intends to aggregate qualitative and quantitative information about this type of technology, studying whether it is economically viable in the market or not. For that purpose, three criteria for a theoretical project evaluation will be assessed: Net Present Value, Internal Rate of Return and the Levelized Cost of Electricity. The later will be compared with the Levelized Cost of Electricity for overland photovoltaic plants and for combined cycle power stations, and with Iberian Electricity Market price. Due to the uncertainty of the cash-flows projections, a sensitivity and risk analysis will be conducted for a more robust interpretation of the results. Two possible locations were chosen in Portugal for the analysis, namely Venda Nova and Pracana hydro power plants. Economic indicators achieved demonstrate that the project is not economically viable for both locations. Considering a 25-years economic life, levelized cost of electricity for Venda Nova 129 €/MWh and for Pracana is 114 €/MWh, being a less competitive generating technology than overland photovoltaic plants and combined cycle power stations.