Here are two plots based on 39 trips where I recorded starting SoC, miles driven, and ending SoC.
Reassuringly (because you never know with those JLR software people), SoC and kWh correlate extremely well, presumably because JLR directly calculates SoC from the same kWh charge estimate they make available via their API.
So: for those of you who don't have access to the kWh figures, going to your MyEV panel and looking at the percentage SoC is a fine surrogate for kWh and you can calculate your range based on current consumption (or historical consumption if you want an average) with this simple formula:
miles_traveled / (StartSoC-EndSoC) = Predicted total range on a full charge
[remember to convert the SoCs to a fraction, i.e. 40% = 0.4)]
Two use cases:
1. You want to know your average consumption for past trips. Just add up all the miles traveled (numerator) and add up all the SoC differences (denominator). Then do this calculation (which is the same as above): Total_Miles / SoC_Sums = average range.
2. You want to know whether you're going to make it to your destination and you've had a headwind since you started. Do the calculation. It will tell you your total predicted range, assuming the current conditions don't change. Then take your current SoC and multiply by the predicted range. That's how many miles you have left. Example: I started at 80% SoC. Have driven 30 miles and it dropped to 65% SoC. Range = 200 miles. That means that now that I'm at 65% SoC, I have 130 miles left in the tank. The GoM shows 150 miles. IGNORE THE GoM. You have 130 miles left. Good thing home is 100 miles away so you're fine either way.