But carrying around an engine big enough for decent acceleration is also inefficient. A smaller engine for cruising plus the hybrid system to give a kick to acceleration can be more efficient than a big engine.
There are laws relating to the conservation/conversion of energy. The air car idea is about one thing. Defying them. Just like electric cars. They are pie in sky feel good nonsense.
Put a 700ft lb diesel engine in a 6000 pound F350 and you get mileage near 20 mpg. Put a 1000cc engine with 80HP in mostly plastic car and maybe you get 40-50 with a tailwind.
The micro car struggles to climb hills or accelerate. It cannot transport enough groceries to feed a family of 4 for a week so you make multiple trips. It cannot accelerate quickly and as you have to floor it to get any performance, components are stressed and wear faster thus requiring more frequent replacement.
It requires many composite materials and other lightweight tricks all of which cost more and require more energy to produce than steel and diesel.
the entire econobox has a limited lifespan and hits the scrapper far quicker, again consuming energy for it’s recycling.
In the mean time, the big Ford is good for 300,000 miles, does not struggle in traffic, can make fewer trips because of greater carrying capacity, uses more easily obtained materials such as steel and diesel and is easily recycled in the big picture by comparison.
Over the lifetime of the two, the econobox takes more energy.