Can someone help me understand the reported kWh usage in the Model 3 menu. I have the LR RWD. I charged this morning to 80% and went for a drive. I travelled 81.5km and the battery dropped to 55%. Energy used is shown as 14 kWh. This was all within the span of a couple of hours and I only spent maybe 10 minutes parked in the car.
If I am consuming 25% of the battery and using only 14kWh, that would mean that at full capacity I only have 14/0.25 = 56 kWh? If I understand correctly the LR battery should have a capacity of 75kWh?
Am I missing something or is there something wrong with my battery at only 20,000km mileage?
There may be, but it is very hard to say for sure, if you are displaying %.
You should switch your battery display at least temporarily to miles/km, rather than %.
It's possible you have a lot of battery degradation, if you spent no significant time in park as you say. Or you may have had some insane vampire drain for unknown reasons (seems unlikely). 10 minutes of maximum heating (if it's getting cold for you) would result in a
lot of drain though - so if your 10 minutes spent in park was at the beginning of the drive before the car was warmed up, that could be a contributor to the result.
Your trip meter numbers should extrapolate to about 71.5kWh for an undegraded battery for a discharge from 100% to "0%" (quotes because 0% is not actually 0% due to the reserve). Yours extrapolate to ~55.6kWh as you say. (Note that 71.5kWh is not the battery capacity - it's more like 79kWh for an undegraded battery, but that's another topic.)
Assuming you had no heating drain while in Park, it looks to me like if you switch to km, you'll see about 408km at a 100% charge, or 326km at 80% (rather than an undegraded result of 521km/417km). Meaning: your battery has lost 21% of its original capacity.
An undegraded battery would lose only 19.5% of its capacity for a 14kWh discharge, rather than the 25% you saw.
Switch it and see. It's sufficient to read the %, switch to km, and read the km. Then report both of those numbers.