This work evaluates the effects of the replacement of engine-powered vehicles by electric vehicles on carbon dioxide (CO2) emissions and energy consumption. A case study of a taxi fleet replacement was conducted with the aid of the AVL Cruise software. The simulation was performed under different scenarios of total or partial fleet replacement along a period of 15 years. The scenarios were designed considering favorable and unfavorable conditions for electricity production from a clean source, thus influencing the CO2 emission factor adopted. The simulations showed that the electric energy consumption by the electric vehicles is about four times lower than fuel energy consumption by the conventional vehicles undergoing a standard test schedule. At the end of the period considered the electric vehicles will produce lower CO2 emissions than the conventional vehicle fleet by a factor of 10, even considering the most unfavorable scenario of electric power generation. An economic analysis shows that the present value of electric vehicles over the years is lower than that of conventional vehicles, except for the first year after vehicle acquisition.