The energy-saving efficiency and CO2 emission reduction when converting from the traditional buses using the internal combustion engine (ICE-bus) to electric buses (E-Bus) depend on the operating conditions in each area. This paper presents a method to calculate the energy consumption and CO2 emissions for E-Bus and ICE buses operating in Hanoi’s inner-city districts, based on the Parametric Analytical Model of Vehicle Energy Consumption (PAMVEC). Experimental data were collected from E03 bus routes representing the typical operating conditions of Hanoi’s inner-city traffic during peak and off-peak hours. Two calculation scenarios are provided: one using ICE-bus and the other using E-bus. The comparison along Hanoi’s E03 route reveals that the E-Bus transition annually saves 80% of energy consumption and reduces CO2 emissions by 32.4% from vehicle operations.