At an altitude of 2,500 meters in the Swiss Alps, near the Muttsee dam, 4,872 bifacial solar panels have been installed as part of a project named AlpinSolar. The installation, which covers part of the dam, has shown that up to 43% of its annual electricity production was achieved during winter, according to measurements conducted between October 2022 and September 2023. Bifacial solar panels are designed to capture sunlight on both their front and back sides, increasing their efficiency. The project's design includes a 1.5-meter gap between the solar panels and the dam to allow for inspections and to enable the panels to capture light on both sides. Snow surrounding the installation reflects light toward the back of the panels, contributing to an annual optical gain of about 1.5%. The high-altitude location benefits from less frequent fog and colder temperatures, which improve the electrical efficiency of the solar power plant. The panels are tilted at 51 or 65 degrees, allowing snow to slide down the lower parts of the dam and not hinder production. This setup results in 68% more electricity production compared to a reference installation near Payerne in the plains. In winter, the high mountain power plant is up to four times more efficient than its low-altitude counterpart. Despite these advantages, the AlpinSolar project does not meet the criteria for a Swiss subsidy program called Solar Express, which requires an annual production of at least 10 GWh and a winter production of 500 kWh per installed kilowatt. While AlpinSolar exceeds the winter production threshold, its annual output is approximately 3 GWh, which is below the required minimum. Additionally, high-altitude solar installations face challenges such as construction costs, access to sites, and connection possibilities. The AlpinSolar project was able to use an existing electrical connection on the dam, which facilitated its operation. However, the construction involved significant logistical challenges, including the delivery of equipment by helicopter and the on-site assembly of a crane used to install the panels. The Muttsee project is considered a full-scale experiment to better understand the potential of solar power in mountainous regions, particularly for increasing electricity production during the cold season. While it does not qualify for subsidies, it provides valuable data on the feasibility and efficiency of high-altitude solar installations, which could inform future projects in similar environments.