having driven a Prius on a long trip and gotten over 50 MPG, I was impressed. AND the electricity was generated by the car, not by plugging it into the wall where the electricity has coal and oil as a usual source.
Some things are a constant in the science world, energy used, etc. How we put the parts together to conserve weight- so it uses less energy to move the mass, all helps to make things more efficient. An all battery car carries a lot of mass, a hybrid, some batteries, a lighter engine, etc, reduces the need for the added energy to move the greater mass.
Just the move from cast iron engines to aluminum blocks has made a big difference in fuel efficiency for many cars.