Tesla cars use induction motors. The rotors of an induction motor don't supply their own field, but need to be excited by current in the stator, which requires

Tesla cars use induction motors. The rotors of an induction motor don't supply their own field, but need to be excited by current in the stator, which requires power. In addition, once there is a field, it produces hysteresis losses proportional to the speed of the motor. If the motor is completely off, the losses from freewheeling are very small. Cars based on permanent magnet motors do not need to use power to maintain the rotor's magnetic field. On the downside, the field cannot be shut off, so they always have hysteresis loss and cannot freewheel as nicely as induction motors can.