I'm curious about the scaling of efficiency of a as you increase power, volume, and mass. I've been thinking about it since Elon mentioned a Tesla truck. Trucks tend to have a significant amount of mass, and when towing or carrying a heavy payload, the mass is increased even more. But with regen, mass isn't the issue, motor/regen efficiency is. The energy required to move an object one location to another depends on the potential energy at each location, not the horizontal distance between the locations. In the ideal frictionless vacuum loved by the writers of physics test questions, altitude change is the only thing that changes the energy requirement for a given vehicle. If you travel to a destination at the same altitude, no energy is required, if you travel to a higher destination, energy is lost, if you travel lower, energy is gained. But we don't live in an ideal world. When you run a motor, or run it in reverse to gain electricity, some energy is lost. If you run it hard, more is lost. What I am looking for is information on how this inefficiency scales. If you were to create a motor with relaxed mass and volume constraints that could provide twice as much torque, how much more energy would you have to provide? If you were to get linear scaling, or near linear scaling, creating a bigger vehicle with more towing capability and more cargo capacity wouldn't decrease range too much. The dollar cost would increase, but range wouldn't drop significantly. The ways energy exits the system are by air resistance and drag, rolling resistance on the tires. and loss due to the inefficiency of the motor and due to the regenerative brakes. Increasing volume increases the cross section, which increases drag, but the increase is small relative to the change in power. Drag also depends on speed, not mass, which means that a heavier vehicle will lose less energy to drag as a percentage, because if you assume the same shape, drag is the same, but kinetic energy at speed has increased. Increasing the weight of the vehicle may increase the rolling resistance of the tires, but again, I don't think that is a major problem. The biggest loss as I see it is due to the motor's imperfect efficiency. In the model S, and other EVs, if you accelerate aggressively, you lose efficiency. The maximum output of the S motor is less efficient than half of its output. Imagine you had a motor that had twice the maximum output power. If you used half of it's capability (the maximum output of the S motor), what energy would it require? Would it be less than the S? more? the same? If it is less, then large vehicles could be more efficient, and creating something like a pickup truck, or even a freight vehicle would come down to choosing the right size for the application. If bigger tasks are accomplished with greater efficiency (though they take more energy), then any application is approachable. If I am missing an important factor, please chime in. In short, it takes more energy to accelerate a heavy vehicle, but more energy is available in the heavy vehicle when you slow with regenerative braking, so large BEVs should be feasible, at least from a physics perspective.