Rising fuel costs, the obvious climate changes and the dangers of the nuclear power lead to a new energy and environmental awareness. Here, renewable energies like wind energy and photovoltaic play a major role. The grid integration of the greatly fluctuating and poorly predictable electricity generation however provides significant challenges for the energy companies. To compensate the poorly predictable electricity production of renewable energies some new concepts and a sophisticated usage of the power plants are required. To analyze the conditions and the impact on an increased proportion of renewable energy sources, the optimization model HiREPS was developed at the Institute of Energy Systems and Electrical Drives of the Technical University of Vienna under the project title AutRES100. The power plant operation optimization program allows the investigation of different energy types, possible memory expansion options and the energy transmission networks. For this model with hourly resolution, accurate data of individual power plants and corresponding facilities are collected and processed. Historical weather data and energy prices enable a realistic analysis of existing power plants and possible future scenarios. This paper deals mainly with the optimisation of the Swiss hydropower plants. For this model all relevant technical, hydrological and geographical data of the power plants and their associated waters were determined. One of the main points was the exact reproduction of the power plant utilization, also high-resolution drain time series of recent decades have been implemented. Extensive simulations of the spot market price and a specific future scenario with 90 percent decarbonisation should show the fluctuating operation of hydropower plants of Switzerland more accurately. Here, the more fluctuating storage and pumped storage operation at increased share of renewable energies could be demonstrated.