I do have an electric vehicle with a seperate meter (modbus) behind the main (DSMR) meter in my house.
However charging power is 11kWh and a storage capacity of 70 kWh so it totally overwhelms the energy consumption of your house. Hence it would be nice if we could deduce the house energy consumption profile as a seperate graph in the energy card.
I think the implementation could be pretty much straight forward as the car actually could be treated as a battery system. Although I cannot yet discharge my car back to my house, but there are already cars that provide that functionality. I assume that there is an entity somewhere in the back that represents the house energy consumption, otherwise it would not be very hard to calculate.
If I define my car as a battery system the power that flows into the battery is plotted negative similar as my PV installation. This seems a bit odd to me ass it is consuming power at that moment.