The order, placed by RATP Dev London, one of the city's principal operators, is for 195 single- and double-deck buses.
With this order, RATP Dev London strengthens its commitment to TfL's electrification plan for London's bus network, which is expected to see all TfL buses become zero-emission by 2037.
Currently there are more than 400 BYD ADL electric buses in London, which have cumulatively covered more than 20 million zero emission miles.
RATP Dev London is set to become the capital's largest operator of electric buses by the beginning of 2022, with nearly a quarter of its London United and London Sovereign fleet fully electric.
Deliveries of this latest order will begin this summer. RATP Dev London's Fulwell, Harrow and Shepherd's Bush depots will host 68 BYD ADL Enviro200EVs – including 21 compact 10.2-metre models – and 127 BYD ADL Enviro400EVs, serving routes in the west. They will join 36 existing BYD ADL single-decks and 29 BYD ADL double-decks delivered over the last three years.
Catherine Chardon, managing director of RATP Dev London, said, "Electrification is a critical part of our business and partnership with Transport for London (TfL). We launched our two first 100% electric routes less than two years ago, as well as London's first fully electric 24-hour double-decker bus route last year. By the beginning of 2022, we will operate 15 zero emission routes and have five of our garages converted to electric. This agreement will help RATP Dev London position itself as the leading electric bus services provider in the city. We are proud to work hand in hand with TfL to help London achieve its sustainability goals."