Regen is not an energy source. An unplugged PHEV takes all of its energy from gasoline, so it's just an ICE car with implementation details. Regen improves ove

Regen is not an energy source. An unplugged PHEV takes all of its energy from gasoline, so it's just an ICE car with implementation details. Regen improves overall efficiency by 3%-10%. It has a relatively small effect even in BEVs. Majority of the energy is lost to rolling resistance and drag (otherwise you could just turn your engine off and coast to your destination…), so there isn't that much to capture. I'm not sure if it even cancels out the extra weight and inefficiency of PHEVs having two power trains. It makes less of a difference than variability between ICE models, so you could be better off driving a smaller pure ICE car.