Thought I'd graph a direct comparison of the electrical watts supplied into a motor and the actual motor output (watts) power.
Based on a 750w motor at full throttle ...


At 1mph energy efficiency is ~3% ... 97% wasted heat.
Flat line at low speed is the A, (= Amps), limit of the controller.
A lower Amp controller reduces waste at low speed without affecting higher speed performance!

Best ... response?
Pedal assist getting started ... and up to more efficient speed?

Data provided by ebikes.ca/simulator