Retrofitting diesel buses with electric powertrains is the next big business in automotive, Wrightbus CEO and ex-Lotus boss Jean-Marc Gales has told Autocar.

He estimates that 34,000 diesel buses will need to be converted or replaced by 2035, creating “a huge business opportunity”.

Northern Irish firm Wrightbus – owned by Jo Bamford, son of JCB boss Anthony – has launched a new sub-brand called Newpower to cater to this predicted demand with a programme that will retrofit diesel bus fleets at their mid-life point.

The company, which built London’s New Routemaster hybrid double-deckers, has opened a new 45,000sq ft facility in Bicester, which it says can convert up to six buses every three weeks.

Each bus costs on average £200,000 to convert whereas a new fully electric bus, such as the recently revealed BYD BD11, costs 500,000, the firm says, having taken bookings through to the end of 2025. 

“We can take buses that are five to nine years old and decarbonise them in just three weeks, giving them an extra 10 years of life,” Gales said. “This is nothing short of a revolution.”

He added: “We wish there was some funding from the government. That would be ideal. But for now, this is the best and most cost-effective way for our customers [to lower emissions].

“We want to convert them all.”

The firm is currently in talks with Transport for London to convert its Routemaster buses, a potentially cheaper route for TfL to hit its 2030 EV bus fleet promise.

If Wrightbus is successful, this contract would begin next summer, truly setting the firm on a “pathway to growth”, according to Gales.

“It would be a coup, a great signal, for us. We made them; imagine if we then repowered them,” said Gales.

Retrofitting ageing diesel-powered commercial vehicles is already big business. UK-based company Bedeo, for example, has created a range-extender electric powertrain for vans. 

Costing around £25,000, it consists of two in-wheel electric motors. These can be selected, and the engine turned off, when the driver requires.

The Newpower conversion process involves replacing the diesel engine with an electric drivetrain that comprises four 77kWh battery packs, and a Voith electric motor on the existing rear axle, for 322bhp and, most importantly for a 10-tonne-plus bus, 1770lb ft of torque.

Front and rear heat pumps are also added to boost efficiency, as well as extra battery cooling and, to cope with the additional weight from the packs, a package of chassis reinforcements.

Range will average 143 miles, depending on passenger loads and use cases, Wrightbus said. For operators wanting more range, a fifth pack can be added into the nearside wheel arch, boosting range to 178 miles. Wrightbus quotes a 150kW maximum DC charging rate.

However, the conversion does reduce bus passenger numbers by around six for the four-pack option and 12 for the five-pack.

Currently, conversions are limited to Wrightbus’s Streetdeck buses, with its Gemini 2 model next up. Each packaging design for a new bus takes six months to create at a cost of £1 million and the firm will also push to convert buses from rival companies.