As I understand it, the home charger does not directly charge the car. It provides AC energy to the onboard charger which then regulates how the charging occurs in the best interests of the long-term life of the battery. The trouble is that the onboard charger can 'bottleneck' at currents above 40A and so they give the buyer the option of purchasing the "Dual Charger" option which allows a greater current through to the battery. The Tesla Superchargers are different. As I understand it, they provide DC directly to the battery (bypassing the onboard charger) and thereby bypassing the 'bottleneck'. Thing is though: Rather than give the purchaser one option at purchase time only - ie, Factory Fitted Dual Charger - why not give the owner of purchasing his or her own supercharger for home. I mean at the time of purchase, one may only have single phase, no plans for extreme use of the car etc... But then circumstances may change. One may get three phase, and want to supercharge the battery from the comfort of their garage. So, why not home superchargers?