An electric bus is a bus that is propelled using electric motors, as opposed to a conventional internal combustion engine. Electric buses can store the needed electrical energy on board, or be fed mains electricity continuously from an external source such as overhead lines. The majority of buses using on-board energy storage are battery electric buses (which is what this article mostly deals with), where the electric motor obtains energy from an onboard battery pack, although examples of other storage modes do exist, such as the gyrobus that uses flywheel energy storage. When electricity is not stored on board, it is supplied by contact with outside power supplies, for example, via a current collector (like the overhead conduction poles in trolleybuses), or with a ground-level power supply, or through inductive charging.
As of 2017, 99% of all battery electric buses in the world have been deployed in Mainland China, with more than 421,000 buses on the road, which is 17% of China's total bus fleet.[1] For comparison, the United States had 300, and Europe had 2,250.[2] By 2021, China's share of electric buses remained at 98% while Europe had reached 8,500 electric buses,[3] with the largest fleet in Europe being Moscow.[4]