Btw, it doesn't matter if the car is towed or not, it takes energy to turn the alternator. There is drag EVERYWHERE on an automobile from the wind resistance to the tires on the road to turning the alternator. You can NEVER produce more energy than you use to do the work AND create the energy (with current technology). Sure, you can coast downhill and turn an alternator or regenerative brakes but eventually, the hill flattens and you have to go and how did you get to the top of the hill in the first place? Energy was spent getting you there to start and that counts. The ONLY pretty much free lunch for a car is solar. Solar charging while parked.