The influence of electric wheeling-mutual accommodation of electric supply through an electrical grid-on both economical and energy-saving properties of cogeneration systems installed in multi-areas is investigated. An optimization approach is adopted to evaluate a critical influence of electric wheeling and to determine the systems＇ sizes and operational strategies rationally. Equipment capacities and maximum contract demands of utilities in each area are determined so as to minimize the annual total cost of the total system in consideration of operational strategies for energy supply to the respective areas and mutual electric wheeling. Numerical studies are carried out on the total system with fuel cells by restricting the total number of mufti-areas to two. The results show that the introduction of electric wheeling brings little reduction of both the annual total cost and the annual primary energy consumption, in spite of reflecting the optimal utilization of fuel cells through the wheeling function.