Earlier quoted context omitted.
Right. And electric motors are more efficient at higher RPMs. At high RPM, the voltage drop due to back-EMF (i.e. actual work) is higher but your voltage drop due to coil resistance is about the same, so you lose proportionally less energy in the form of coil resistance at higher rpm.
> electric motors are more efficient at higher RPMs. How big is the difference? It must be pretty substantial to offset both friction losses and gearing efficiency.
Consider that at ~0mph and ~0rpm, producing any kind of torque at all is done with ~0% efficiency, all just resistive losses as the back-EMF is effectively zero. (Note this is no different for an internal combustion engine, although the heat generated is in the clutch or similar such device...)
Friction losses don't change much as a proportion of power as you increase speed. For aerodynamic drag, however, your losses do proportionally increase with speed, so "windage" (i.e. drag from spinning parts of the motor) needs to be cleverly reduced by making the rotor aerodynamic if you're planning on operating at high rpm.
EDIT: for properly designed electric motors (i.e. thin wire windings, iron core optimized for low eddy current losses), coil resistance usually dominates even at high rpms.