The increase of greenhouse gases (GHG) in the atmosphere forces the power industry to reduce the use of fossils fuels, aiming a Carbon-free energy production. Wind and Solar power plants have been deployed to reduce GHG emissions. However, these technologies occupy big land extensions on a utility-scale. This suggests the use of open water surfaces to install large photovoltaic (PV) floating plants. In this paper, a country-size hydro-solar power generation model is proposed. PV is more predictable than wind power, which already enters the grid without dispatch. This research intends to evaluate if Hydroelectric Power Plants' (HPP) reservoirs can host, near their dams, PV Floating Power Plants (PV-FPP) sized to meet the hydro capacity. Then, use the synergy of hydro and solar sources to run a hybrid generation model. To achieve this goal, we established the state-of-the-art of floating PV generation in Brazil and the world from academic and technical literature. We identified and described the solar characteristics, calculate the PV potential, and simulate a hydro-solar model. This resulted that Brazil can replace its 2020 fossil thermal generation using 50% of the proposed hydro-solar model potential. This model on all country’s HEPP can add 84.5 TWh/year to the electric system.