The prospect of a renewable transition seems plausible for many countries, but can be shrouded in risks, costs and challenges. This paper illuminates a path for such a transition with a numerical investigation, aimed at resolving the power dynamics of a country powered only by renewable generators. The focus was Switzerland, with its considerable hydropower infrastructure and plans to phase out nuclear energy. The model uses optimal power flow calculations to compute the transmission of electricity, and also accounts for the movement of water within the hydropower system. Results suggest that the renewable goal is attainable and will not require radical re-building of the country's transmission infrastructure. Under our assumptions, it was found that the transmission grid is placed under slightly lower stress on average, in renewable scenarios. Despite matching supply and demand on average, the fully renewable system required a ∼ 107% increase in electrical exchange with neighbouring countries to compensate for seasonal variability, and additional intermittency of electrical supply. Simulation results are described for three scenarios: Current, Intermediate, and Renewable. The bulk power statistics, temporal dynamics, distributions of line use, and spatial patterns are presented, and the implications of the results are discussed.