Real-world performance of battery electric buses and their life-cycle benefits with respect to energy consumption and carbon dioxide emissions

Battery electric buses can reduce energy use and carbon dioxide (CO2) emissions in China's transportation system. On-road testing is necessary to evaluate these benefits compared to their diesel counterparts through life-cycle assessment for both the upstream fuel production and operation stages. Three electric buses from China are operated and charged in Macao under different air-conditioning, load, and speed settings. In the minimum load scenario, the two 12-m buses achieve 138-175 kWh/100 km, and the 8-m bus achieves 79 kWh/100 km (system charging loss included). When air-conditioning and load are at their maximum values, the energy consumption increases by 21-27%; however, air-conditioning usage exerts a greater impact than passenger load. The diesel bus on-road performance increases more significantly than the electric bus performance under low speeds, higher load, and air-conditioning use, while the electric bus energy and CO2 emission benefits increase. Across a wide range of conditions, the electric bus reduces petroleum use by 85-87% compared to a diesel bus and achieves a 32-46% reduction in fossil fuel use and 19-35% in CO2 emissions from a life-cycle perspective. A cleaner power grid and an increase in system charging efficiency (if better than 60-84%) would enhance the future benefits of electric buses.