Abstract—The challenge of converting the fleet consisted of conventional buses with more modern vehicles is particularly up-to-date nowadays. In this paper, it is assumed that – sooner or later – only Battery-Electric Buses (BEB) will operate the bus routes. The content includes a basic structure of the algorithm supporting the decision process of bus fleet conversion, from the currently operated conventional or mixed fleet to the fleet consisting of electric buses only. In the algorithm, three major paths are derived, which results in the following indications in terms of the conversion process: vital technical parameters of electric buses, a comprehensive schedule for the bus fleet conversion process and the economic assessment of the investment in this technology. An outline of the decision support tool for the deployment of electric buses using the energy consumption model to calculate the total cost of ownership is presented in this paper.