Mercedes' first-ever production fuel-cell vehicle, the B-class F-cell, will go into limited production within weeks.
The first 200 models could be built next month and will be delivered to customers who have leased it in the US and Europe soon after.
Dr Thomas Weber, head of research and development, told Autocar at the Frankfurt show, where the car was unveiled, production will start "in several weeks".
Mercedes claims its hydrogen-electric hybrid is comparable in performance to a 2.0-litre petrol car, but its zero-emission powertrain can manage the equivalent of 86.6mpg on the combined cycle.
The electric motor produces 134bhp and 214lb ft of torque. Its range is around 250 miles and it takes three minutes to refuel the car with hydrogen. By comparison, a 1.8-litre petrol B-class (no 2.0-litre petrol model is available) produces 114bhp and 114lb ft of torque in B180 BlueEfficiency SE guise.
The German firm has addressed one of the weaknesses in existing fuel-cell vehicles which is the ability to perform cold starts. The B-Class F-cell can start in temperatures as low as minus 25 degrees Celsius - lthough its Honda FCX Clarity rival is able to start from minus 30 degrees Celsius.
A 35kw lithium-ion battery is used to store any power wasted under acceleration, recovers energy lost under braking and it provides back-up power to the electric motor.
Interior and boot space are both unaffected by the addition of the F-cell powertrain. The boot’s capacity of 416 litres is the same as a regular B-class and the drive components are stored in the floor. Safety is also unaffected, with the system undergoing 30 crash tests prior to production.
A Mercedes statement said: “2009 is the year in which we are establishing further milestones where sustainable mobility is concerned. The B-Class F-cell is taking on a pioneering role as the world’s first fuel cell powered automobile to be produced under series production conditions.”