I have started to do this myself using data available from the car and WattCat.
Everyone should consider using the App once it is widely available.
At the beginning of each trip I log the following.
kWh available in battery (from WattCat)
SoC % start
At the end of the trip I record
kWh available end
I can then calculate what the car thinks I used by multiplying avg kWh/100km * km traveled /100
I can compare this to the actual powered used according to WattCat available charge start - available charge end.
(The two results are always different)
And I can compare km traveled against estimate range used in the course of the trip.
The answers are very revealing and in my case disappointing.