The need to decrease greenhouse gases emissions in the transport sector has resulted in the requirement for zero emission technologies in city centre bus fleets. Currently, battery electric buses are the most common choice, with both single deck and double deck vehicles in regular use. However, long-term operational capabilities are still largely unknown and unreported. Hydrogen fuel cell electric buses are an emerging zero emission technology that have the potential to complement a battery electric bus fleet where the duty cycle is challenging for current battery electric configurations. This paper compares the difference in energy consumption, for a given chassis configuration, passenger load, and heating requirement, of generic battery electric and hydrogen fuel cell electric buses operating in a typical UK city environment. A methodology was employed that will provide bus operators with a robust mechanism to inform buying decisions, based on their route characteristics, when transitioning to a zero-emission fleet. Simulations performed using battery electric and hydrogen fuel cell electric models showed that the hydrogen fuel cell electric bus has a much higher predicted range (465 km) and operating time (23.1 hours) than the battery electric equivalent (273 km and 13.5 hours) when considering a duty cycle of mixed city operation. While the hydrogen fuel cell vehicle showed limited variation in the range across all drive cycles considered, the battery electric bus showed a high percentage decrease (16.4%) in range when subjected to drive cycles with higher average road gradient. Meanwhile, when considering operation on a drive cycle with 0% average road gradient, the battery electric bus was predicted to have a percentage increase in range of 12.5%. This study shows that when considering a zero-emission vehicle technology mix, the characteristics of the service routes should be considered before deciding which powertrain configuration to utilise on each route.