Sadly almost impossible to calculate Mick.
First factor that prevents calculation are the hills that are ridden, since hills are the main place where weight counts, on the flat it hardly matters.
The second variable is the amount of rider input, since the level of input directly decides the amount of motor power added, and hence the consumption.
The third variable is which gear each rider uses on this system at any one time, since the pedal speed (cadence) also determines power levels input.
And the fourth variable that can differ between riders is when the High or Eco power modes are used.
This explanation gives more detail on that.
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