Electric Bus Basics
Similar to the battery electric vehicles (BEVs) discussed on the Vehicle Types page, battery electric buses (BEBs) and electric school buses (ESBs) run on electricity only and require recharging their onboard battery packs from an external power source.
The average range for BEBs and ESBs varies based on the battery pack capacity and is significantly impacted by weather, driving behavior of the operators, topography, and ridership load.
For more detailed information on BEBs, ESBs, and their charging infrastructure, see the Transit Cooperative Research Program’s “Guidebook for Deploying Zero-Emission Transit Buses” and the National Renewable Energy Laboratory’s “Electrifying Transit: A Guidebook for Implementing Battery Electric Buses.”
Battery Pack Size
BEBs are categorized as long-/extended-range or fast-charge depending on the size of their battery packs. Long-/extended-range BEBs have larger battery packs (250-660 kWh) and are meant to only be charged once or twice per day. In contrast, fast-charge BEBs have smaller battery packs (50-250 kWh) that can receive more frequent high-powered charges.
A type of BEB, ESBs tend to have smaller battery packs as they often operate on shorter routes with a midday break during school hours for charging. Because of this use pattern, ESB equipped with bidirectional batteries are also uniquely suited for Vehicle-to-Grid (V2G) or Vehicle-to-Building (V2B) arrangements in which the ESB provides energy storage that can moderate the cost of electricity during peak times, store power generated from intermittent renewable sources, provide backup power in case of power outages, and ultimately bring financial benefits to school districts as they sell power back to the grid.
Three Types of Charging Infrastructure
There are three types of charging infrastructure for BEBs, all of which can be installed at the maintenance or storage facility (depot) or on-route: plug-in charging, wireless inductive charging, and overhead conductive (pantograph) charging.
Plug-in Charging
Plug-in charging has both AC and DC options to charge at a low power (40-125 kW). The number of buses accommodated will depend on the configuration of chargers and ports, which are often installed in depots, as buses are generally charged for multiple hours or overnight.
Larger batteries typical of BEBs (250-660 kWh) require long charging time at low power. There are a number of faster (up to 350 kW) plug-in charging solutions available for transit vehicles.
Even faster plug-in charging options are under development, with a 1 MW standard introduced in summer 2022.
Wireless Inductive Charging
Wireless inductive charging uses floor-mounted receiver pads that are charged using a magnetic field produced by a transmitter embedded in the roadway. This system uses a low to medium power level (50-250 kW).
Overhead Conductive Charging
Overhead conductive (pantograph) charging requires a physical connection between the charger and the onboard battery through a pantograph apparatus or overhead wires.
In-service electric buses can be recharged through a pantograph charging system while stationary in 5-20 minutes at a higher power level (165-600 kW). In-motion charging (IMC) trolleybuses, which use overhead catenary wires installed on only 20-40 percent of the bus route and otherwise use battery power, charge at a low power level while moving.
Electric Mobility Infrastructure Planning for Urban Areas contains more information about transit electrification planning, including cost considerations regarding charging infrastructure.
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Electric Mobility Basics
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