Greener cartalk, now that the Hydrogen FCVs have lost traction, is focused mainly on electrics. But the way a car runs is only half the story. Another way to green a car is to cut the amount of energy a vehicle needs to run in the first place, and for many automakers this has become a big focus.

To keep energy consumption low, carmakers have entered a race to shrink the automobile without sacrificing space. Now that the Smart has celebrated its first decade, there is growing competition for small. Toyota has released the "world's smallest four-seater" the iQ. They claim it's not just a small car, but a groundbreaking one and they have managed to pack a lot in less than 3 meters (117.5 in).

Another way automakers are cutting energy use is by completely rethinking a vehicle's design. Renault's Z.E. (Zero Emissions) concept treats the car like a Thermos flask. The bodywork is made of insulating panels to sandwich air in between which acts as an insulator. Add to this heat-reflective paint and acid green windows that keep direct heat out and you've got a car that doesn't rely on much external climate control, though there are solar panels on the roof to power what little AC or heat the passengers may need.

It seems carmakers are also learning from hypermilers about how to cut energy use and are now offering drivers "eco" options, whether through driving indicator lights (as on the Z.E.) or by offering the option to let the car do the work for you. With the 3rd generation Prius, when a driver switches to Eco Mode their throttle movements will be smoothed out to maximize gas mileage (AC is also put on efficiency auto pilot).

In this video, we visit the Barcelona Motor Show for a peek at the Z.E., Prius III, iQ, Tata Nano and Peugeot's 3-wheeled hybrid scooter concept, the Hymotion3 Compressor.