I am not really sure what you are calculating here. That being said I am pretty sure that the model s has a 270mi RANGE, not a 270kWh battery. It has a few options, like 85kWh or 70kWh. It has been published that the model 3 will have a smaller battery, and be a smaller car. Being more efficient at the vehicle level, coupled with cost savings of vertical integration, will allow use of a smaller and cheaper battery.
