Volkswagen has created a concept of its Up model which features plug-in hybrid technology.
The Twin Up uses a diesel-electric powertrain similar to the one used in VW’s futuristic XL-1.
The new concept features a more powerful electric motor and a greater-capacity lithium-ion battery to cope with its greater weight (1,205kg).
The motor has been uprated from 20kW to 35, while the battery storage is 8.6kWh instead of 5.5.
The company is quoting fuel consumption of nearly 256mpg for the car, compared with just under 314mpg for the XL-1.
The respective CO2 figures are 27g/km against 21g/km. The powertrain pairs a 50bhp, 800cc two-cylinder diesel engine - half the engine in a diesel Golf - with the electric motor and a seven-speed DSG gearbox.
The car can run in full electric mode for up to 37 miles at a maximum 77mph, as a hybrid with a combined 75bhp and 215Nm of torque, or as a diesel at speeds of 90mph. It has a range of close to 700 miles using both power sources.
Charging the battery from empty takes two hours using a standard domestic socket. Battery power can be reserved until needed, such as when entering cities where there are emissions taxes.
At the moment the Twin Up is only a study, but it has been designed so that it can be built on the same production line as the combustion-engined and electric versions of the Up if there is sufficient demand to make a business case for it.