This study aims at exploiting optimal configurations of technologies combined with co-generation theoretically based on a linear optimization model. With the objective function defining primary energy consumption to be minimized, optimal solutions are derived analytically. They describe the technological configurations as well as associated conditions depending on their final energy demand. An interesting finding is that the essential parameters to determine the configurations are heat, cooling and steam demands normalized by power demand. The optimal solutions are also applied to investigate the competitiveness of co-generation related technologies. The optimal solutions yield critical conditions theoretically, which is useful to understand the priority of the technologies. A sensitivity analysis numerically indicates that absorption chillers can be superior to compression chillers even though the former has lower COP than the latter. Actual data of various types of co-generation are also examined to show the practical competitiveness. (C) 2010 Elsevier Ltd. All rights reserved.