My current car has "regenerative breaking" that charges the battery(not a hybrid, just a normal BMW). I haven't tried any testing without cruise control on, bu

My current car has "regenerative breaking" that charges the battery(not a hybrid, just a normal BMW). I haven't tried any testing without cruise control on, but with cruise on it will definitely do a little breaking on highway downhills to maintain speed. Every generation of car is getting better at all these things, so statements about efficiency almost all need a "cars built prior to 20XX".