In a workshop in the eastern German city of Erfurt, a 10-year-old bus has had its diesel engine removed in preparation for a refit. The new electric engine is waiting to be installed.

"It looks easy but is very high-tech," says Hans-Georg Herb, head of Elerra, a local firm that specializes in converting regular vehicles into electric ones.

The former engine bay now has enough space for batteries.

"We can install eight battery packs with a capacity of roughly 200 kilowatt hours, which is enough for the bus to travel around 250 kilometers (155 miles)."

Herb says turning diesel buses into  electric ones isn't just fascinating from a technical point of view, he also believes it makes economic sense.

Depending on the battery, converting a regular bus into an electric one costs between €300,000 ($296,000) and €340,000, which is roughly half the cost of a new one.

"We want to get three more buses done this year," he says, adding that he's aiming for around 70 in 2023. 

More e-buses on the road 

 The EU's Clean Vehicles Directive is pushing demand for battery-powered buses in urban transport. Around 15,000 buses across the EU, and 3,000 in Germany will have to be powered electrically in the coming years, according to some estimates. And large manufacturers are struggling to keep up with demand.  

E-buses could be a money saver for transport companies because they require less maintenance. Driving with electricity is also up to 60% cheaper than using petrol.

Declining battery prices and increased mass production of components have made converting petrol-powered vehicles to electric ones more attractive.

"I can imagine that more than half of the buses that are currently driving will be converted one day," Herb says. "If we want to manage decarbonization, we won't get it done without this kind of conversion."

Is it worth converting cars as well?

Swapping out combustion engines for electric motors is technically possible for all cars. It requires the removal of the old engine and gearbox to make way for the electric one and batteries. Engineers have to develop specific electric steering systems for each car.

The first car Herb converted was a Porsche 911 back in 2014. He caught the bug and started transforming even older cars into e-vehicles, before moving onto buses.

Converting a vintage car costs around €60,000, Herb says and points to a black Jaguar Daimler limousine from 1993.

"The customer wants to have it electric. In this case, we'll use Tesla modules," says Herb. 

Assembly kits to install e-engines and batteries for vintage cars cost at least €10,000 and require more than 100 hours of labor. The technically minded who want to take on the project themselves can save a lot of money and pay companies like Elerra to simply advise them.

But Herb says converting classic cars isn't worth it from an economic perspective. 

"Vintage cars don't usually get driven a lot, so operational costs don't matter as much. Converting them is more of a hobby."

And he has a similar take on smaller normal cars. Herb says he regularly has to advise customers that buying something like a Volkswagen e-Up electric vehicle would be cheaper and better than converting an existing VW Polo.

 "It doesn't really make sense to convert a VW Polo and I have to stress that point often."

Converting cars for the city

Alongside the buses, three new trucks are waiting to be converted in Herb's workshop. One of them is a Mitsubishi Fuso mini truck, which is only available with a regular combustion engine for now. 

Herb's team is converting the vehicles to electric four-wheel drives. Each will be fitted with batteries and specially designed software.

"These vehicles are really good for driving in winter and that's why we are working on a small series of electrically powered four-wheel drives for cities," says Herb.

His is not the only workshop in Germany or Europe retrofitting regular vehicles with e-motors. With European cities working to decrease air and noise pollution, and following the new EU climate protection rules, there's plenty of work to be done. 

Even delivery companies, such as UPS, are increasingly converting regular vehicles to electric ones. 

This article was originally published in German.