I noticed today when I was partially charging my new P8 that the charger was recording more KWhs than would have gone into the car. I was going from 70% to 90%, so 15 KWh. However, my home charger reported delivering 16.7 KWh. I noticed something similar with a short term rental electric car. Is this normal behaviour? Could it be related to difficulties related to charging in the higher % ranges - maybe requiring more energy to condition the battery or something?
Charging Question
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First off, there are energy losses between the cable and the car. Secondly, the battery is actually 78 kWh but only 75 kWh are usable; how accurate those two figures out might also have some variance, I'd assume. I'd also assume some of the figures you saw have some rounding involved. Though 10% off seems quite a bit -- but I'm not engineer 
I've read that 90 percent efficient is normal. Our xc40 seems to be better than our Bolt when it comes to charging efficiency. Our bolt is particularly bad when it is colder and it is charging to less than 100 percent. I no longer keep it plugged in due to this perpetual drain once at the target level and because barbequed garage/house is not something that I am interested in. Also with only a 1 percent resolution we know within 1500ish watts of what it used. Example: Does the car charge to just barely 80 percent or just shy of 81 percent. When it reads 51 percent did it just change down from 52 or is it about to go down to 50. So... Using 20 percent (80 to 60) could really be a almost 81 down to just over 59 (16.5 kWh) or a heavy 79 down to light 61 (13.5ush kWh). Plus the inefficiency of charging... 90 to 70 and pulling 16.7 from the wall is reasonable.
If I recall correctly, someone had already performed some tests which revealed that this car was be able to achieve around 95% charging efficiency using level 2 in the summer.
Was your car locked the entire time when it was charging? I usually lock the car (mirrors folded inward) before starting my charging session. That way some stuff will be turned off quicker after getting out. Whereas the worst case is if you go back and sit in the cabin with the climate control, seat and steering wheel heaters on, less power will go to the batteries, and it will take longer thus consuming more power.
I am happy that the charging efficiency has been around 95 percent at 240V x 30 amps. We usually charge to 80 percent, though when I was parked at a work location with free charging I filled up to 90. The bolt tended to be 85 to 90 percent efficient charging.
It was locked almost all of the time. Since the car is new and this was my first time charging it (need to play with my new toy!) I went out a couple of times to see what was happening since the app was not updating SoC as frequently as I expected. But this was only for a minute at a time.
I don't know how quickly the app updates, but there will be no minute to minute change. With 240x30 amp charging the battery charge should increase by 1 percent every 6 to 7 minutes. 120x12 amp should increase about 1.5 to 1.9 percent per hour (if no battery heating or cooling is happening).
I’ve got a 7 kW charger (which was running around 6 kW as it approached 80/90%), so I was not expecting minute by minute change, but the app seemed to update only in fits and starts, and a couple of times only updated to show a few % increase when I unlocked the car.
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I’ve noticed sometimes the app doesn’t update SOC at all, and will show the same % it started with throughout an entire 4 - 5 hour charging session.
And in the end it's not the "app" - it's the car's software/hardware plus Volvo's server/comms infrastructure. The mobile app is just a lightweight display client, but it can't display data that the server doesn't have.
The same mobile app seems to work reliably on non-EV, non-AAOS vehicles.
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