The total kWh is from App under Charge Stat tab. I installed L3 wall charger at home garage before the car delivery. It has all daily charge info. The power (kWh) delivered for each charge session matches with shown on car screen when the cord was detached based on my observation.
The energy number shown in the car as +kWh, (which also is used for example in teslafi and I guess several other apps) will show a higher number than the actual charged energy that entered the battery.
The reason is that the range the car shows at 100% includes the buffer but as the SOC reduces the car progressively hides a part of the battery capacity so at 0% we have a 4.5% buffer below 0%. Only 95.5% of the battery capacity is between 100-0%.
During a charge this buffer is “unhidden” so each percent more charge means 1/0.955 of the battery capacity is displayed.
This means the on screen charging exaggerates the charged energy with 1/0.955 ( 1.047 = 4.7%)
This can be seen with softwares that can show BMS-data. The +energy will be 4.7% higher than the change in nominal remaining energy in the BMS.
This also makes that for example teslafi shows a charge efficiency that is about 4.7% too good.
When I measure the energy with a extern electrical meter mounted just before the WC I more or less always get ~10% more energy than the change in nominal remaining.
At the same time the displayed + energy is 4.7% higher than the increased nominal remaining, so the efficiency of the charge looks too good.
On top of this there is another loss when driving that depends on battery temp and power used. Sometimes (summertime) I see about no loss there, the nominal remaining and the delivered energy is about the same) and for faster drives or colder battery it can be 1-2%.
The difference between delivered energy and “recharge energy” in the EPA tests is about 12% for most Teslas tested, so we should expect about that efficiency (energy use when in park not counted here, just the real charged energy compared to when driving when looking at the trip screen energy)
Started last October, the app added Home Screen that provided charge stat for each session.
The current drive and since charge power usage reported by the car seems to be quite often off in my car so all these “vehicle standby” numbers shown up. I also have observed quite inconsistency in the power numbers. For example, I did a round none-stop item pickup trip at 107 miles away (all interstate driving) for a total 213 miles a few days ago. Started at 100% SOC with preconditioned car, got back home @ 8% power left. The car reported the trip used 67 kWh power. The pickup stop was only 15 minutes so no SOC change was observed (@55 %). If this is true, my car would only have 72 kWh battery total power. But after I charged the car back to 80%, 58.2 kWh was added. This would suggest I have a 81 kWh battery.
67kwh for 92% = 72.8kWh “usable”, so 76.25 kWh total capacity.
Charging back to 80% means 72% of 76.25 is reported as +energy so the screen should say 55kWh (54.9 rounded).
The real change in battery energy would be 0.955 x 54.9 = 52.4kWh (can also be counted as 72% of the usable 72.8).
The energy drawn from the wall should be about 52.4 / 0.9 = 58.2kWh (a bit depending on the charge power. Full 11kW AC charging causes low losses by shortening the charge time.)
So I guess the 58.2kWh you refer as added is the drawn energy from the wall?
Anyway, after all these efforts, I just accepted the uncertainty of the Tesla BMS is part of life. It would be impossible to achieve the efficiency Tesla claimed (but I got great efficiency (220 kw/mile) for 40 miles behind a 18 wheeler on an interstate driving but it is too much a gamble to do unless I want to get a broken windshield soon). Tesla is a fun car to drive & my kids love it with all these high tech features.
The efficiency Tesla clames is by the EPA rules and is not expected to be achieved in anyday driving. It is not impossible at low speeds on a warm day, but we should not expect that to happen most days.
