This study examines an experiment in energy self-sufficiency in Seoul, Republic of Korea, through a particular energy policy called the One Less Nuclear Power Plant (OLNPP) policy. We define an urban energy experiment as a purposive intervention for energy transition from an energy system based on nuclear and fossil fuels to one based on renewable energy and energy demand management. We suggest three findings. First, we find that the themes of our theoretical framework policy backgrounds, governance and policy contents have played important roles for Seoul's energy experiments aimed at urban energy autonomy. In particular, political leadership based on the mayor's previous experiences contributed significantly to the formation and implementation of this policy. Second, the OLNPP policy adds a social or moral dimension to urban energy policies. The norm change from an environmental and economic focus to a focus on the combination of social, environmental, and economic considerations is a unique contribution of the OLNPP policy to urban experiments in energy transition. Third, we find that experiments through purposive interventions serve as a means for facilitating urban energy governance where the actors involved can communicate and enhance their new ideas and practices. (C) 2014 Elsevier Ltd. All rights reserved.