UK-based bus manufacturer Alexander Dennis said on Wednesday it will begin trials of a factory-supported retrofit programme in 2026 to convert existing diesel buses to electric drivetrains, starting with the Enviro400 double-decker model. The initiative, called ‘AD Repower’, will be conducted in partnership with clean transport technology company KleanDrive.
The repowering service aims to provide bus operators with a cost-effective and environmentally friendly alternative to replacing diesel fleets with new electric vehicles. The trial will begin in the UK in the first half of 2026, with future expansion to additional models and markets depending on demand.
The conversion replaces the diesel engine and transmission with a modular electric drivetrain centred around the Voith Electrical Drive System (VEDS). The system will be powered by a 352 kWh lithium iron phosphate (LFP) battery supplied by Chinese battery manufacturer CATL. According to KleanDrive, the retrofit can deliver a range of up to 195 miles (314 km) per charge under standard operating conditions with a 50% passenger load.
“By repowering rather than prematurely replacing, we avoid throwing away a perfectly good vehicle and the carbon dioxide that is embedded within that,” said Joe Tighe, CEO of KleanDrive. “This is a great solution for operators and the environment.”
The retrofit maintains the original interior and seating capacity of the bus and is designed for on-site installation at operators’ depots. It integrates with existing vehicle controls and can be maintained by local technicians, according to the companies.
Chris Gall, Group Engineering Director at Alexander Dennis, said the programme complements the company’s zero-emission product line. “We believe that offering new electric buses as well as repowering vehicles already on the road is the quickest route to decarbonisation of our customer’s fleets,” he said. “Their drivetrain engineering is in keeping with our reputation for quality.”
Alexander Dennis, a subsidiary of Canadian bus maker NFI Group Inc., joins other manufacturers exploring electrification retrofits. Competitor Wrightbus launched a similar initiative, NewPower, last year using the same VEDS drivetrain but with NMC battery packs.
While Alexander Dennis has not disclosed pricing, Wrightbus previously estimated the cost of a comparable retrofit at around £200,000 ($255,000), offering a more affordable pathway for operators to electrify fleets ahead of traditional replacement cycles.