European national, regional, and local authorities have started to take action to make public bus transport services more effective and less polluting. Some see the possibility to move beyond a narrow focus on efficiency or carbon dioxide reductions towards an integrated sustainability perspective. This paper uses this perspective to build and test a new assessment approach that should enhance decisions on bus transport powertrains and energy carriers for Swedish medium-sized cities. The study suggests that a superiority of electric powertrains is revealed if a traditional economic analysis is integrated with a strategic sustainability perspective.