Charging forward: How bus availability drives the economics of fleet electrification

The electrification of bus fleets is central to achieving low-carbon transport, yet uncertainties remain around whether electric buses can deliver reliable and cost-effective operations for all types of operators. While previous studies emphasise their lower fuel and maintenance costs, limited attention has been given to the economic implications of vehicle downtime. This study investigates how electric bus availability influences fleet size requirements and subsidy needs. Using detailed maintenance and downtime data from a UK bus operator, we apply a total cost of ownership (TCO) framework combined with a probabilistic model of bus availability over a 20-year period. Our analysis shows that although electric buses incur lower maintenance expenditures, their reduced availability substantially increases the number of spare vehicles required, raising capital costs – especially for smaller or rural operators. For example, electric fleet size requirements increase by roughly 18 to 23% per 10-percentage-point shortfall in availability relative to the diesel fleet benchmark. Policy simulations indicate that that if availability has not improved since 2020, then today’s operators will require procurement grants of between 35.7 and 45.0% depending on the scale of operation – and will continue to require additional financial support beyond 2040. Whereas, if availability has and continues to improve, the procurement grants required by today’s operators fall to between 30.7 and 39.7%, with no procurement grants necessary past 2032. These results highlight that vehicle availability is a critical but underappreciated factor in fleet electrification and should be explicitly incorporated into both cost analyses and subsidy design.