This study presents the intermediate findings of a two-year Design Science Research project aimed at developing and refining design principles for a persuasive Decision Support System tailored to households adopting dynamic electricity tariffs. Using survey data and choice experiments, we define context-relevant design principles that are both grounded in empiric design theory and actionable. Based on such, we then present user interface mock-ups. Future research will systematically evaluate the design principles and the interface prototype. In additional design cycles, the system’s backend will be integrated with the interface and tested in real and simulated environments. This study contributes to the body of literature on the intersection of behavior-focused system design and sustainable energy solutions, offering prescriptive knowledge to enhance consumer engagement with dynamic tariffs - a success determinant of the energy transition.