A statistical analysis of more than 6,000 energy performance certificates including retrofit options proposed by experts for different building elements is performed. This provides an overview of the most commonly suggested renovation measures and their estimated investment costs and U-Values. Based on an energy model of the Swiss residential building stock (SwissRes), the theoretical energy savings are estimated. Together with the estimated investment costs, the levelized costs of each renovation measure is then determined in order to identify the most cost-effective measures. It is shown that a large-scale energy retrofit of the residential building stock would result in theoretical energy savings of up to 84% regarding the current simulated energy demand. Yet, existing technical and social constraints would lower the expected energy savings significantly. None of the selected measures is cost-effective, but under a more optimistic scenario, the cost-effective share reaches up to 85% of the total potential energy savings.