Electric powertrains increase efficiency in road vehicles and enable zero tailpipe emissions, but introduce practical limitations in on board energy storage capacity, due to the low energy density in battery systems when compared with chemical fuels in tanks. The increased powertrain efficiency and lower on-board energy storage levels place focus on other energy consumers in the vehicle system, such as the braking system. Our measurements indicate that a conventional pneumatic electronic braking system for heavy vehicles consumes 2-3% of the mission energy in a typical city bus cycle for a battery electric vehicle. The newly developed electromechanical braking system offers a more efficient energy conversion for the braking function, consuming 0.4-0.7% of the mission energy under similar driving conditions. This work focuses on an energy analysis of the conventional and the novel system in the context of a city bus application. The data is sourced from measurements of a battery electric bus, driven on a proving ground in tests repeated three times, in unladen condition. The measurements include comparative tests for the vehicle equipped with a traditional electro-pneumatic braking system and the same vehicle equipped with the new electro-mechanical braking system.