@Wamoosh, welcome to the forum!
So, let's take this from the top. When routing a trip with the NAV, the Tesla software in there has a couple-three requirements about how to do this:
- Get you to your destination as fast as possible
- Get you to your destination without you running out of charge somewhere (a related, but significant requirement)
- Get you to your destination so you're not bone-dry when you get there
Let's take these one at a time.
As "fast as possible" runs right up against the fact that a Tesla, when supercharging, charges at its fastest rate when it's near dead empty. If one plugs in a Tesla at, say, a 250 kW charger, one will get that charge rate when the car is down below 20% of full charge or so. After that, it ramps down the rate so, at 80% or so, it's down to 70 kW. So, on long trips with multiple Supercharger stops, with a sufficient number of superchargers around, the NAV software's route planner has one showing up with less than 10% charge (going for that sweet fast charging rate) and has one leaving with 80% or less.. because that last 20% of full charge takes longer than the first 80%! And they're trying to
minimize one's time on the road.
Sometimes this seemingly gets a bit ridiculous: One will get to a Supercharger with a low charge and the software will suggest charging for
ten minutes, then continuing on to the next, ad infinitum. That's barely enough for a bathroom break. But it does get one to one's destination fairly quickly, that being the point. Mostly it's not like that, though: I just got home from one of my periodic trips to Boston and the NAV had me stopping in Charlton for 30 minutes for about a 70% charge, then told me to continue, which I did. That was just enough to get me home with 10% charge remaining, which was why it did that: I didn't have to stop anywhere else, so it took that into account.
Now, onto the next requirement: Not Running Dry Somewhere. That's not so much a factor on the East Coast, where it's getting to the point where if one throws a rock, hard, a few times, one will hit a Supercharger somewhere. But if one is starting off without a full charge, the NAV software is perfectly capable of figuring out where one would run dry and Strongly Suggesting that one stop short of the Run Dry location, or even detour somewhere (not as common as that used to be, thanks to Tesla's gangs of SC installers) in order Not To Run Dry. All this poking around the landscape is
still subject to the idea of getting one somewhere as quickly as possible, so if the trip router can avoid detouring, it will do so.
This kinda feeds into Tesla's printed suggestion that, if one is going on a trip, and in particular if one has home charging set up, charging up to 100% just before one leaves is a Right Good Idea. First, home charging is typically 2X to 3X cheaper than a Supercharger, so kind of avoiding Supercharging is a no-penalty kind of thing if one has home charging. Second, this gives the NAV more flexibility as to where one's first stop might be. It's not a
big deal, since the NAV will get one to one's destination anyway, but what the heck.
Minor point: Tesla's Big Mothership runs an Operations Center. To the extent that they can, they know which Superchargers are full of cars, which are empty, and rough estimates of when all those Teslas roaming the landscape are going to congregate, and where. They'll try to route one to non-full SC's.
In this short list, there's the idea of Not Being Dry when one gets to one's destination. Generally, when one leaves it up to the NAV, it'll tend to get one to one's destination with just enough charge left, for, I dunno, 50 miles or so. Or at least to get to a Supercharger or destination charger somewhere. This is where one's brains are typically called into use. For an (obvious) example, I can make it from NJ to Boston, with a 100% charge, since the M3 I'm driving has a 330 mile range, and it's 250 miles or so from here. But if I get there with 50 miles (or whatever) left over, that means running around visiting relatives is going to get awkward in a hurry.. so I usually stop at some Supercharger within spitting distance of the city and gas up to 80% or so.
Which brings up a minor point: From 0% to 80% on a Supercharger is about 20 minutes. That's not a whole heck of a lot of time, just enough to hit the bathrooms and get a cup of coffee. So that quick stop when one hits one's destination isn't a big deal.
By the by: ABetterRoutePlanner's main claim to fame is that, if one uses the tool, one can put in one's desired charge level when one gets to one's desired destination, and the ABRP will make that happen. I don't use the tool, myself, but there are definitely people out there who are enamored of its features. (ABRP doesn't have the Tesla Mothership's Operations Center.. but it works anyway.)
Finally: You asked about Mileage. Sigh. On Ye Typical ICE car, the usual thing one gets, and the only thing one gets, is a DTE value (Distance to Empty). These are notoriously inaccurate, so much so that hardly anybody uses them seriously. Going up a mountain? Down a mountain? Against a headwind? With a tailwind? Cold weather? Hot weather? None of that is in there. Most people just keep an eye on the gas gauge and try not to run dry in Wyoming somewhere. (I don't want to count the number of cars I've owned over the years where one discovers, over time, that there's one or two gallons of gas in the tank when the gauge reads empty. Sigh.)
Tesla's aren't like that. In spades. Nobody is saying that a Tesla's equivalent of a gas gauge is infinitely accurate - but the collection of stuff presented is good to within +/-2% to +/-5%, which is
much better than what an ICE has to offer.
First, there's the Mileage number at the top of the screen. Tesla gets this by multiplying the amount of charge in the battery times the Monroney sticker value. you have a MY; I believe that most of them have a 78 kW-hr battery and a 280 W-hr/mile rating. So, if one is at 50% charge (39 kW-hr), then that mileage indicator will show 39 kW-hr/(0.28kW-hr/mile) = 139 miles of range.
This is pretty much the most inaccurate of the indicators built into the Tesla. Next up: The Energy Screen.
Looking at the Tesla screen, at the bottom edge, there's an icon with three horizontal dots. Tap that, and you'll get a ridiculous number of icons; games, theater, radio, streaming, it goes on and on. but one of those is labeled, "Energy" and has a kinda plot icon on it. Tap that.
You'll get a window with Tesla's contribution to the Bewildering Plots of the World. But, there's good stuff in there. Along the top edge of this window, on the right, there's a "Consumption" button. Tap that. What you'll get is a plot of energy usage per mile for the last 5, 20, or 50 miles or so. Did you play Drag Strip with somebody five miles ago? You'll see a spike in energy usage. Coming down the Rocky Mountain Rise for 10 miles? You'll see the energy usage go
negative (i.e., the car's absorbing energy to keep a constant speed). Got the heat turned on? More energy usage. Just driving along? A more or less horizontal line. The critical stuff? On the right vertical axis, it'll give you the
estimated range based upon the plot. This is based upon whatever-the-heck driving you've been doing over the selected range and, given a squinty look, will give you a reasonable guess as to how far one can get.
Interestingly, there's a horizontal dotted line from left to right that's labeled, "Rated". That's the Monroney value for your car. On warm months, the energy usage of the car beats the Monroney value, sometimes by substantial. Cold months, it's the other way, a bit. If one plays Jackrabbit Jones on the road, then the energy usage will be higher, but you knew that anyway.
Go back to the top of this window and select the left-most plot. This is a plot trending down from the top left down to the bottom right. There's a more-or-less straight line there; that's the
rated energy consumption. There's a line, usually lower than the rated, but not always, that shows you how you're doing on this drive. But the
really interesting stuff is below the bottom of the plot. This is where the Tesla tells you where All The Energy Has Been Going. Weird driving habits? It's in there. Running at 90 mph? It's in there. Got the heater running? It's in there. Preconditioning for a Supercharger stop? It's in there. Weather? It's in there. There's about six items in there that show you, specifically, what's affecting your range and by how much.
The middle plot in this whole Energy thing gives one information about what has been termed, "Vampire Drain". This is the energy usage when one is parked. People get stressed about this, so Tesla has it out there so one can see.
That ends the Energy Plot discussion. And, now we get to the Most Accurate range estimator the car has.
When one is on NAV and has a destination plugged in, the car calculates its future energy usage and displays a little square window, down near the bottom edge of the screen. In there is the % charge at the destination.
That is the most accurate range estimator, bar none, that the car has. Tesla's software and hardware people have pulled out the Big Guns and Did Their All to make that "% charge at destination" number.
On one's route: Going up a hill? It's in there. Going down a hill? It's in there. Different speed limits on different roads? They're in there. You doing 90 mph? It gets in there, maybe not instantly, but it does get in there. Got a headwind? It's in there. Got a tailwind? It's in there. Using the heat when going over the Donner Pass, but not when one is back in the flatlands? It's in there. Outside temperature? It's in there. Battery degradation? It's a recent update, but it's in there. It's
ALL in there. Really.
If one is double-checking, look at the distance-to-destination number and compare it to the Miles at the top of the Tesla screen, then do a little subtraction to see how much one will have when One Gets There.
Weird, in its way. One Single Number (more or less) To Rule Them All. But that "% charge remaining" is the Good Stuff.
Hope this helps.
