Range-extending technology produced by Tevva Motors which helps trucks emit less CO2 than pure diesel vehicles is on trial around the UK.
The company's technology is featured in the right-hand-drive JAC N Series 7.5-tonners that are being used around the country.
JAC has supplied the Essex-based firm with chassis cabs that it is re-powering and using as rolling test beds.
The Department for Transport and the Department of Energy and Climate Change have helped fund the project.
Tevva's equipment is also on trial with UPS in a Mercedes-Benz Vario in the London area.
It could potentially be slotted into trucks grossing at up to 18 tonnes.
"If we sell the vehicle as a Tevva using a JAC platform then we'll probably be able to get it homologated and into production in three to four years' time," said Richard Lidstone-Scott, business project manage for Tevva.
"A retrofit package suitable for other trucks will hopefully be available on a commercial basis within the next two to three years."
Tevva fits the N-Series with a 120kW/1,800Nm electric motor married to a reduction gearbox that takes the drive to the rear axle via a shortened prop shaft. Power comes courtesy of lithium-ion phosphate batteries positioned beneath the truck's load bed.
The batteries can be recharged from a three-phase 32-amp mains supply in under three hours says Tevva and provide a range of up to 100 miles on battery power only.
If they need a bit more charge while the truck is working then the range-extender kicks in. It's a 100hp 1.6-litre Ford diesel engine that sits beneath the truck's tilt cab and acts as a generator with no direct connection to the final drive.
It lengthens the range to approaching 370 miles depending on how big a fuel tank has been fitted.
The whole system is looked after by a cloud-based package called Predictive Range Extender Management System.
You send it the truck's planned route for the day, it works out how much energy it is likely to burn and the range extender cuts in and out accordingly.
The idea is to ensure that the diesel doesn't suddenly fire up in an urban area when the truck should be relying solely on its batteries to make deliveries without generating NOx and other pollutants. If it is required then it should cut in when the 7.5-tonner is travelling along an out-of-town dual carriageway.