Hey there, thanks for your reply. As i mentioned, my analysis was done on a very light foot, almost no AC, and max regen. So this was not a 'joy ride' experiment. At the end of the day my argument is that the dash board is lying about Wh/mi, as if it actually read the truth, i would accept it. But there is a misleading figure of efficiency that is clearly untruthful. Tesla should be transparent, as it doesn't take much math skills to uncover their lie. I won't sell my Tesla even if it's as inefficient as it is, but Elon is insulting my intelligence here. Best regards
I've taken three long road trips in five years. I've found the range used per leg to be very close to what is reported. Less than 10% inaccuracy. How are you measuring the real energy you claim the car used? If you are going by how much energy the car took on at the supercharger, it may be you got a supercharger with a problem and there was high resistance loss while supercharging. ie your car actually took on about 50 KWH of energy while supercharging, but the supercharger put out 69 KWH and 19 was lost in the equipment. That is a problem with that one supercharger and not a problem with your car or anything endemic to supercharging.
Tesla is better with their superchargers now, but back in 2016 I spoke with a tech at a supercharger when I had problems with slow charge rates on my trip. He said they were having problems with superchargers aging too quickly and he spent most of his time replacing parts that were wearing out from excessive heat. As they broke down, one of the failure modes was they tended to develop higher electrical resistance, the cables and handles would get very hot (I ran into this) because of resistive heating.
Every model of Tesla needs to go through EPA testing where they put the car through a standardized testing regime. Other countries have their own testing regime for determining real gas mileage/range. Most manufacturers base their range/gas mileage claims on the results from the testing agency. Occasionally a car maker may sandbag and claim less range or poorer gas mileage than the tests, which I believe has been the case with some EVs. However I believe there are laws against claiming more than the testing agency reports.
Most cars sold in both Europe and the US have better claimed range/gas mileage in Europe because the European agency's tests are not as close to real world conditions as the EPA and they come up with better numbers. In most cases the difference is around 20% if I remember right, though I know it differs from car to car.
On the highway EVs tend to do worse than their EPA rating because the EPA test focuses more on how people tend to drive in cities than on highways and EVs get their worst efficiency when driving at high speeds, whereas ICE tend to get their worst efficiencies in stop and go traffic (than regen for that).
I have read the criteria of the EPA test and for EVs they take into account the losses while charging the car (though they only charge the cars on AC), so they look at how much energy the car drew from the power mains, not how much went into the battery.
AC charging and DC charging do have different losses. If you charged a Tesla at the same rate as you do with AC charging, it would be more efficient than AC because the electricity goes directly into the battery and bypasses the AC charging equipment which has some losses (though the latest generations of AC chargers are way up in the 90%s for efficiency). DC charging has losses from electrical resistance anywhere along the line. Supercharger cables are thicker than AC charging cables in an attempt to keep I^2R losses down.
Copper has the lowest resistance of anything we know of in the temperature range we humans live in. There are superconductors that have zero resistance, but the best superconductors quit working above the temperature of liquid nitrogen. Kind of useless for everyday uses. So we use a lot of copper for electrical uses. Copper still has resistance though and it mounts up when you put a lot of current through it, the power loss goes up with the square of the current.
Batteries also get hot when you charge them fast due to their own internal resistances. If you've hung around a Tesla while supercharging the cooling fans and coolant pumps start going nuts after about 10-15 minutes because they are pumping coolant through the battery pack to cool the batteries.
Relatively low power DC charging is very efficient, but at the sorts of powers you draw from a supercharger, there are losses. Though losing 19 KWH to get 50 is excessively high and tells me that something was probably wrong with the individual supercharger you used.
I have free supercharging, so I've never had any indication how much energy was used to put energy in my battery pack. I would not be surprised to see 5-10% equipment loss while supercharging, but over 30 tells me something was wrong with the charger. I would try and contact Tesla because you were overcharged for their faulty equipment.
None of us can tell if theres an issue with your car...can only offer feedback from our own experience.
Like I said, my efficiency went from 50-90% just by adjusting my driving habits.
Good luck to you figuring this out, hope you get it settled.
I thought I was a pretty efficient driver when I got my car. The first year my Wh/Mi was around 320, but since my MCU upgrade it's under 270 (it bounces around in the high 260s).