Energy consumption is the main cause for greenhouse gas emissions, which need an active mitigation in the coming decades. Industrial countries, like Austria, have assumed responsibility by sharing international endeavors, like the Kyoto protocol and the EU 2020 targets. Austria already has one of the highest shares of renewable sources in electricity generation, of which the main part is produced by hydropower. The basic idea of this master thesis is to determine the investments needed to increase the share of renewable power, up to a full replacement of the fossil plant park until 2030. The analysis starts with the structure of primary energy sources as the traditional transformation input for the electricity system. For reshaping the Austrian electricity system, the future development of electricity demand is estimated, which depends not only on the growth of real GDP but also on possible shifts in final energy consumption towards a higher share of electricity. For covering the growing electricity demand, the potentials from renewable sources are examined and defined. For the case of Austria, the focus of the analysis lies on hydro, biomass, wind, and solar photovoltaic sources. Many different factors are influencing the costs of electricity generation. Thus, for determining the investment needs, it is necessary to answer the question of economic feasibility of an on-going transition to renewable power technologies. Only if the cost gaps are closed by adequate support mechanisms, e.g. feed-in tariffs, the investments will take place in real life. The structure and efficiency of such policy instruments is a pre-condition for the transition to renewable electricity, but not part of this paper. In the scenario model developed and used in this paper, the power generation gaps are determined upon different trend paths of electricity demand growth, combining its outcome with the successive reduction of fossil power over the next twenty years. The investments needed are calculated by using specific investment costs of renewable power technologies, which until 2030 decline according to the technological progress rates. To summarize the abstract, the author of this master's thesis intends to answer the following main questions: What is the range of the future development of electricity demand? What are the key factors of influence for the transition to renewable power generation? What are the investments needed until 2030 for a renewable electricity system in Austria? The author's motivation to address these questions origins from his confidence that Austria is one of the few countries in the world that can proof the feasibility - economically and technically - of an electricity system based on renewables, and hereby demonstrates to the world the possible solution of the looming climate and energy problems. The author, himself being employed by a large international banking group, hopes that his results and conclusions may convince many financiers and investors that the transition to a renewable electricity system opens up large business potentials with relatively low risks.