Life cycle analysis (LCA) using the process chain analysis (PCA) approach has been widely applied to energy systems. When applied to an individual energy system, such as coal or nuclear electricity generation, an LCA-PCA methodology can yield relatively accurate results with its detailed process representation based on engineering data. However, there are fundamental issues when applying conventional LCA-PCA methodology to a more complex life cycle, namely, a synchronized life cycle of interconnected energy systems. A synchronized life cycle of interconnected energy systems is established through direct interconnections among the processes of different energy systems, and all interconnecting systems are bounded within the same timeframe. Under such a life cycle formation, there are some major complications when applying conventional LCA-PCA methodology to evaluate the interconnecting energy systems. Essentially, the conventional system and boundary formulations developed for a life cycle of individual energy system cannot be directly applied to a life cycle of interconnected energy systems. To address these inherent issues, a new LCA-PCA methodology is presented in this paper, in which a new concept of partial temporal boundary is introduced to synchronize the interconnecting energy systems. The importance and advantages of these new developments are demonstrated through a case study on the life cycle of the coal-uranium system. (C) 2015 Elsevier Ltd. All rights reserved.