Technology Connections also did a video on this.
The basic conclusions I got from it in terms of efficiency:
-
Conventional hydrid cars are not all created equal, with parallel hybrids typically being more efficient than serial hybrids
-
Plug in hybrids are frequently less efficient than a well designed conventional hybrid, if they are not charged regularly by electricity
-
Both are very inefficient compared to battery electric vehicles by nature of engines being inherently inefficient