A large expansion of renewable energy is key to zero-emissions electric generation, supporting further decarbonization in other sectors, such as mobility through electric vehicles. Utility-scale PV are now among the cheapest ways to produce electricity but require large surface extension, potentially in a conflictual way with other uses. Mountains have usually favourable conditions for solar energy and are, in some part, scarsely populated, but they have a high landscape value and several fragilities. Floating photovoltaic panels over dam reservoirs may provide a relatively inexpensive and highly upscalable increase of electricity supply, with synergies with existing hydro-plants (e.g. in transmission lines). In this work, after a brief description of the system and its general features, building on state-of-art world reports, an evaluation of the potential of Swiss artificial lakes for floating PV installation is explored, with particular attention to a broad and diverse set of social, environmental and landscaping constraints and opportunities. In order to support appropriate decision-making, a set of raccommendations is produced to fit the need of all stakeholders, including local communities, energy experts, businesses and regulators.