I'd say the Rolec figure is the correct one if you want a real world end-end figure.
From the charge point to the battery you will lose about 7-10%. There will also be some losses getting the energy back out of the battery.
As for the additional discrepency it might be down to how the car calculates the mi/kWh figure. For instance, does that include heating and regen.
Ultimately, dont worry about it.... its cheap driving either way and you cant do anything about the losses... they are what they are.
From the charge point to the battery you will lose about 7-10%. There will also be some losses getting the energy back out of the battery.
As for the additional discrepency it might be down to how the car calculates the mi/kWh figure. For instance, does that include heating and regen.
Ultimately, dont worry about it.... its cheap driving either way and you cant do anything about the losses... they are what they are.
