My X P100DL 72 amp charging rate is just 45 miles per hour compared to my S 90D rate at 53 miles per hour with the same charger - is this because the X consumes more power per mile than the S? X 72 amp people - how many miles do you get? By the way, Lucille is a real treat to drive

Your car's instantaneous charging rate is kw. Which is amps x volts = 72 x 233 / 1000 = 16.77 kw (or u can switch the screen to show % state of charge, the kw number is shown on the left). Looks pretty normal if you have a HPWC, it is as fast as it get. the whatever miles/hour "charging rate" is incredibly misleading, and it is the actually the average charging speed over the entire charging session, NOT an instantaneous charging speed. A lot of people who are new to Tesla always get this confused.

Yup as ggnykk pointed out... 72a x 233v = 16,770w or 16.77 kw Charging also has some losses, so it's efficiency is around 90% 16.77 * 90% = 15.093kw 15.09kw / 333 rated wh/mi on X = 45mi hr. 15.09kw / 280 rated wh/mi on S= 54mi hr.

It is not average charging speed over the entire charge, that will actually be a different number of you do that math. It slowly integrates towards the actual charging rate, where the integration time interval depends on how faster you are charging. It's going to basically max out soon after you start charging on a HPWC. edit - integration is the wrong word. It's more like a moving average, but still the averaging interval depends on the current charging speed.

Driving both cars lately makes me appreciate the efficiency of the model S - those falcon wing doors on the X are just non-stop fun though! I've been close to 400wh / mile on the X compared to 280-290wh per mile on the S lately - I can see why the S broke the consumer reports' rating scale when they reviewed it. I have to say the model S is the car for me, all things considered

This is true for DC charging where there is a taper. With AC charging, what you see is what you get. If his car says 45 miles/hr (typical for a Model X at 72A), after 1 hour of charging he will have added 45 mikes of rated range and in two hours 90 miles.

It is not this either. Charging rate on AC charging is practically the only conservative measurements of/in the car. You will typically get more miles than this reads.

With AC charging it's closer, but there are still tapering effects. At the beginning of the charge, the current ramps up slowly so the miles/hr (average) takes a minute or so to catch up to the actual value. And when charging to 100% when balancing kicks in - once the display shows 99% (or however many miles corresponds to 99%) the rate of charge becomes tiny yet the miles/hr average still shows a significant value. I've often heard of people sitting waiting for a 100% charge to finish when they'd have been much better just setting off straight away. Things also get complicated when it's cold enough for the pack heater to get involved, though I don't think any of the instrumentation gives you a clear indication of what's going on in that case.