In this paper, a prototype of scenario-based environmental assessment framework of energy-related technology roadmaps is demonstrated using a case study with particular focus on introduction of electric vehicles (EV). Taiwan plans to promote EV-related industries, setting a quantitative target for introduction to its domestic market. Replacement of vehicles powered by internal combustion engines by EVs will increase electricity demand, which is closely coupled with emission of greenhouse gases and other pollutants. On the other hand, it can contribute positively in removing mobile source of pollutants as well as in load balancing of the power grid. Concurrently, introduction of EV reduces gasoline demand, which requires a shift in the operation of petrochemical industry. Power mix optimization model, consequential model for petrochemical industry, and scenario models for vehicles use and replacement are used in an integrated manner to comprehensively assess abovementioned contributions together with other major factors such as nuclear reactor operation, and promotion of renewable energy and other energy saving technologies. Findings from conducting this case study are summarized for the further development of this framework that aims at providing a common platform for evaluating roadmaps into an integrated picture to discuss their effectiveness being aware of interactions among the technologies.