In recent years, the conditions for the successful operation of E-buses by public transport operators fundamentally changed from day to day. The main reason for this is the tension between climate protection and economic feasibility. The rapidly increasing international awareness on air quality and the stagnation concerning the development of internal combustion engines resulted in a breakthrough for E-vehicles and E-buses. The success of BEBs and FCBs will be assessed based on environmental and economic criteria. Based on the current state of the art in comparing diesel buses with E-buses, only environmental considerations speak for the operation of E-buses. The total operation costs of E-buses describe the biggest challenge that still needs to be overcome. In the meantime, it is important to first conduct an analysis on the electrification potential as well as to ensure promoting and funding by decision makers before a fleet renewal towards E-buses.