Public buses ensure mobility for more than 450 billion passengers annually as a necessary means of transportation in cities around the world. However, buses have an image problem in the eyes of the urban population, because half of the buses in the EU urban transport fleet are in the best case classed as Euro 3 (European emission standards). Consequently, the renewal of bus fleets should be a priority in order to provide sustainable urban mobility. Our paper presents the benefits of replacing diesel buses in the fleet of Compania de Transport Public (CTP) Cluj-Napoca with electric buses and the impact of this change on the environment. Following the introduction of 11 electric buses into urban transportation, to replace the same number of diesel buses this study evaluates and highlights the reduction of CO₂ as the greatest bulk component of greenhouse gas (GHG) emissions. In the context of renewing the public transport fleet of CTP Cluj-Napoca, the present work investigates the quantity of CO₂ emissions removed from city traffic. Currently, in major cities of the world, there are policies to reduce GHG emissions by introducing the electric buses in the public transport fleet, moving toward the gradual replacement of diesel buses.