••Solar energy radiating on high-altitude floating arrays could meet total Swiss demand••Bottom-up modeling combines high-resolution meteorological data with physical model••Solar energy radiating on high-altitude floating arrays could meet total Swiss demand••Bottom-up modeling combines high-resolution meteorological data with physical model••Site suitability tool determines electricity generation across water bodies••All sites are economically viable before subsidies at 0.41 USD/Wp solarThis paper develops a meteorological site selection algorithm to quantify the electricity generation potential of floating solar design configurations on alpine water bodies in Switzerland. Using European power market demand patterns, we estimate the technical and economic potential of 82 prospective high-altitude floating solar sites co-located wi. Energy resourcesEnergy managementEnergy ModelingEnergy SystemsGlobal climate change requires increased urgency and attention in the energy sector to develop low-carbon electricity supply options that can dramatically reduce carbon dioxide (CO2) emissions (Hansen et al., 2016). Across Europe, small countries without large available land resources have developed stringent policies to decarbonize their power sectors, whereas also operating in a space where land is limited for greenfield electricity system development.In particular, Switzerland has committed to transitioning to a clean, net-zero emissions energy system by 2050. Phasing out nuclear power will create an electricity supply gap of nearly 24.4 TWh, implying that without changes in electricity demand, countries such as Switzerland must look to alternative generation options (Swiss Federal Office of Energy, 2018). The number of choices is few – hydropower is facing financial and climate-induced risk owing to hydrologic variability and uncertainty to drought, utility-scale solar requires large land areas, distributed generation requires public buy-in and acceptance, and wind turbines are often located offshore. Therefore, high-altitude land areas could offer promising alternatives to meet carbon goals, reduce the land-use intensity of energy, and take advantage of existing electricity infrastructure, which is costly and often requires long lead-times to build. These systems can also allow existing hydropower to continue to provide flood control or other ser. Previous research identifies temporal mismatches between producing solar electricity and demand consumption in Switzerland (Bartlett et al., 2018). This study provides a methodology to calculate the potential electricity generation from high-altitude floating solar sites, based on geographical characteristics and panel attitude. To date, no study has evaluated how the electricity produced from floating solar PV can be incorporated with Swiss electricity supply and demand patterns and the impact on seasonal mismatches. This study evaluates the extent to which high-altitude floating solar resolves seasonal mismatches in supply and demand. Recent studies demonstrate the considerable potential of solar installation in the Swiss alps; however, these insights have not been applied to floating solar cases (Kahl et al., 2019). This study addresses this gap and applies these insights to floating solar. Many mountainous stretches remain difficult to reach, making it challenging to exploit such solar resources – thus our new research provides a feasibility test to determine whether existing dam reservoirs and transmission system interconnections are accessible for construction. Previous work has not evaluated the potential along water bodies, and has only considered land-based PV systems. In this study, we also develop a bottom-up approach to determine electricity generation potential that can be applied in other countries with high altitudes and existing hydropower dam reservoirs. Previously, these infrastructure systems have not been systematic.