The emissions of CO₂ gas caused by transport in urban areas are increasingly serious, and the public transport sector plays a vital role in society, especially when considering the increased demands for mobility. New energy technologies in urban mobility are being introduced, as evidenced by the electric vehicle. We evaluated the positive environmental effects in terms of CO₂ emissions that would be produced by the replacement of conventional urban transport bus fleets by electric buses. The simulation of an electric urban bus conceptual model is presented as a case study. The model is validated using the speed and height profiles of the most representative route within the city of Madrid—the C1 line. We assumed that the vehicle fleet is charged using the electric grid at night, when energy demand is low, the cost of energy is low, and energy is produced with a large provision of renewable energy, principally wind power. For the results, we considered the percentage of fleet replacement and the Spanish electricity mix. The analysis shows that by gradually replacing the current fleet of buses by electric buses over 10 years (2020 to 2030), CO₂ emissions would be reduced by up to 92.6% compared to 2018 levels.