This chapter reviews the theoretical and empirical literature on smart city performance and its relationship with the energy transition, and explores the challenges associated with assessing environmental performance in smart cities of the Association of Southeast Asian Nations (ASEAN). More specifically, it proposes a framework for evaluating smart city performance in the context of smart cities situated in Malaysia. The study constructed an environmental performance framework (EPF) consisting of eight indicators, comprising a total of 23 items. Our analysis indicates that the mean EPF score for firms in smart cities is 21%, representing a fraction of the total maximum achievable score. The results suggest that concerted efforts are required from both governmental bodies and businesses to facilitate firms’ contributions to the energy transition within smart cities.