Pursuing a sustainable energy transition at the city level represents a significant strategic aspect in the worldwide movement toward climate change mitigation and carbon neutrality achievement, as global cities account for large proportions of global energy consumption and emission. The current study explores the direction of future energy production and energy systems projecting to 2050. Data were collected from experts in the energy industry and the policy of Busan Metropolitan City, and these data were analyzed via explanatory factor analysis. The results pointed to four factors of future energy production: renewable energies, fossil fuel, bioenergy, and ocean energy. Four factors of future energy systems were also identified: prioritization on mobility and building, the role of actors, interactions between energy producers and consumers, and small-scale production. In general, for future energy production and systems, the experts strongly supported low carbon-intensive energy and distributed generation, respectively. It is also important for the various actors, such as policymakers, producers, and consumers, to be integrated to achieve sustainability and carbon neutrality. An interesting result is that the political orientation of experts led to different preferences, particularly regarding nuclear energy. •A case study of Busan is examined to learn the direction of city's energy transition.•Utilization of ocean energy was emphasized along with solar, wind and bioenergy.•Energy system on mobility and building/factory should be prioritized.•Role of actors (i.e., authority, business, producer, and consumer) is important.•Perception on nuclear is varied based on the political orientation.