As a master student of renewable energy living in Vienna, it is naturally interesting to know, if my own city would be able to base its energy system fully on renewable energy produced within or around the city. But the answer should be more than a theoretically yes or no. It should also give an indication on costs for the individual household and necessary steps to achieve this goal. To reach a scenario of 100 % renewable energy I first analyzed the potentials to reduce energy demand in the main sectors households, service sector, industry and mobility. Thereafter the reduced demand split by energy carrier is compared to the potentials for renewable energy within the city and around it. Finally in a combing model the effect on costs for households for energy services are simulated in 2 scenarios. The first important result is that it is indeed possible to supply Vienna with 100% renewable energy produced within the city, or in its surroundings by using only little resources of its neighboring state, Lower Austria. The second result was that especially some of the saving measures will strongly increase the costs for energy services of households. The main conclusions are that there is a significant potential of renewable energy to be used within and around Vienna at reasonable costs. But to really reach a 100% renewable scenario, it will be necessary to support especially households in the area of energy demand saving for space heating and mobility.