There's nothing in the comms between domestic 3.6/7 kW EVSE & the car that relates to this. All that gets passed is the car says "I want power" and the EVSE says "You can have X amount of amps" and that's it. So to do what you want, either it has to be something completely outside this kit, so app talking to car etc, or you would need some smarts added to the EVSE so you could tell it what the SOC was at the start of a charge, and what the battery capacity is. The EVSE could monitor how much power goes into the car, and in principle it could learn how much it takes to get to 100% charge, and that way it could learn what the charging efficiency is. But whether any of them do this, I don't know. Would eb an interesting diy project to build though!