It’s really more of a misnomer that nothing reaches 100%..
I’d be interested where all the data comes from, is it TeslaFI or track my tesla?..
Anyway, it’s very hard to take a number like AVERAGE MPH, and extrapolate clearly or that precisely. Directionally, this is all probably accurate. Higher speeds, lower “efficiency”.. lower speeds, SOMEWHAT higher efficiency.
But, for example. We’ve seen many many tests, either early on or since M3 launch that the highest “efficiency” is ~ 31-33 mph. A LR M3 can do economy of ~ 115w/mile. That would yield about 600+ miles of range. Traveling constantly and flat without significant excess weight other than TWO occupants.
That is technically 210%+ efficiency. i know from having done speeds like that on purpose that I can get the level of economy from the battery and motors.
Having done many tests on I5 traveling when there are no significant elevation changes, doing 30-60 mile runs, resetting trip computers and measuring battery % and range, watching the onboard measurements I can get 110% efficiency at ~ 65 mph and roughly 100% at 70 mph. but with acceleration, hills, slow start stop start this all changes and overall it drops to ~ 90% efficiency. On these longer trips I also tend to travel quite a bit at 80+, averaging somewhere between 72-75 over hours at a time.
As an example if I drive from home to town 1.3 miles each way and back again, no elevation changes.. moving the mass in reverse, then starting forward, then coming to a stop, then moving all the mass again up to 33 mph, is about 40% efficiency, driving at 33 mph (with total average of 25) is ~ 175% efficiency. Overall, it’s about 115% at the end.
So, while these mph numbers are averages, there probably aren’t enough captured trips, of long enough duration that were really JUST at 30-35, or 35-40, etc to make the real efficiency at those speed ranges more precise and evident of what the abosolute efficiency is at that fairly specific speed.