Innovative, but I question the need and additional complexity.  Is it really value added?    Hard to be fuel conscious in a sports car.   Maybe for a mini van.   

The write-up states that Mazda claims a "five-percent improvement in efficiency", but, is that an improvement in fuel efficiency or in the energy consumption efficiency of the car's charging system?  Do the vehicle's electronics really consume over 5% of the fuel burned?  I agree, Glen... is this really value added in a Miata?

@flying-dutchman

I read a couple articles about this system. It seems small and lightweight, using capacitors, which are ancient technology,  so it should be cheap and simple. 

If it powers the electronics, reducing the drag of a burdened alternator,  it may add 5% fuel efficiency.  The Skyactiv already makes a difference.  My NC gets 24.5 mpg over 5,000 miles. My RF gets 30. That is 20% more efficient. 

I have an even better idea... get an NA!  Minimal electronics to gobble up electrical power 😉.