My Model 3 (dual motor long range AWD, Fall 2018) uses significantly less energy when it is on autopilot than when i drive the same roads at the same speed myself, as gently as possible, and using the single pedal (in standard mode)? On autopilot, which I use only on freeways or well-marked roads, it gets the rated mileage (245-250 Wh/mile, leading to a 310-mile range). I can drive the same roads myself, going almost exactly the same speeds, trying to mimic the autopilot's driving as closely as I can, and I do 10-20% worse. Does anyone know the reason for this difference? Does the autopilot route different amounts of power to the two motors as a function of speed and incline differently from what can be achieved with the accelerator pedal?
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Why does my Model 3 use significantly less energy in self-driving mode?
- Thread starter mpstryker
- Start date
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- Tags
- energy consumption
You know the difference between the black bar and the green bar regen right?
I bet it's because your driving with your foot uses more power ie more black bar then the smart ai autopilot. It would be interesting to see a video recording of the same route with both videos next to each other to see the comparison but I bet autopilot is just better at using regeneration then you are.
Also, I don't care how good you are. Your speed is probably more variable then the locked in autopilot speed and more variable speed will be less efficient.
ElectricIAC
Good-Natured Rascal
Interesting. My AP seems to be horrible at using regen except in the lightest deceleration. Really loves the friction brakes it seems.
Daniel in SD
(supervised)
If you're driving efficiently on freeways you really shouldn't be using regen or friction brakes.
ElectricIAC
Good-Natured Rascal
Yeah but who buys a Tesla only to stay in the right lane doing 55?
Daniel in SD
(supervised)
Someone who wants to get 240-250Wh/mi. haha
Not sure what speed has to do with using the brakes though. I suppose if you're aggressively weaving through traffic it would be necessary.
ElectricIAC
Good-Natured Rascal
My guess is that almost any kind of cruise control saves energy on both ICE and EV cars because your speed is constant. Especially at the end of long trips your instinct is to drive faster due to being tired and wanting to finish the drive. I can't imagine it would be as much as 10-20% unless you are varying your speed on manual over a wide range constantly. Personally I have not noticed any particular energy savings in Autopilot though I do arrive at my destination feeling less tired.
dsnows
Member
Time to admit the truth... it's a better driver than you.
Daniel in SD
(supervised)
It takes slowing down.
I do see people using their brakes/regen while sitting in the left lane on the freeway so I know what you're talking about. I just give them a little more distance so I don't have to and we both get there at the same time.
CharleyBC
Active Member
On level (-ish) ground, true. But try driving on I-80 from Donner down to Auburn, CA or so on AP. You'll be green bar much of the way, and actually adding substantially to your SOC as you go. Lotsa regen!
CharleyBC
Active Member
That's the crux right there, I bet. As humans, we are more variable than those darn computers.
AlanSubie4Life
Efficiency Obsessed Member
It is super difficult to make these comparisons. My guess is assuming the driving is fairly similar (no brakes), the difference is actually minimal. Do you have comparative data with the exact conditions (historical weather data, time of day of drive, climate settings, average speed, traffic conditions, length of drive, max speed, state of charge, actual consumption, etc.)? If the sun is shining vs. it being overcast on a cool day, same temperature, and you are using any heat, it would make a huge difference, for example.
If you have a chance, do another experiment and log the data carefully. Definitely turn off climate control completely - it will be impossible to determine what is happening if you have AC or heat on. Obviously the route and conditions have to be identical.
Regen, and inconsistent driving, definitely could be a contributor but if you are driving the same as autopilot that’s not going to be a factor (most humans are better than autopilot - if they try).
I think a lot of it has to do with regen. When my car is on AP it almost never hits the friction brakes. Instead with the distance set a 2 or 3 it starts regening earlier than I would to maintain the gap time. And we know regen alone can add 30+% to range over friction braking.
AlanSubie4Life
Efficiency Obsessed Member
The OP said he was mimicking AP as best as possible. Which might well mean more regen than necessary. But it should be easily possible to drive more efficiently than TACC. Perhaps not over the long term, but certainly if you are trying to drive efficiently it should be easy to do much better than TACC (but I doubt it would significantly impact efficiency due to diminishing returns - TACC is fairly efficient).
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ElectricIAC
Good-Natured Rascal
My right foot starts to hurt if I’m too easy on the throttle.
Autopilot creeps over the speed limit less often than you do, so loses less energy slowing back to the speed you have set.
Also, it doesn't creep up on cars in front of you as much as you do, so doesn't slow down to back-off so often, which, again, loses energy.
So yes, it's all about consistency.
PS yes, I know in slowing down there is a little energy gained back in regen, but only a fraction of what is washed-off in speed.
Also, it doesn't creep up on cars in front of you as much as you do, so doesn't slow down to back-off so often, which, again, loses energy.
So yes, it's all about consistency.
PS yes, I know in slowing down there is a little energy gained back in regen, but only a fraction of what is washed-off in speed.
Personal experience here, but I have actually been more efficient than the AP. My drive to work, during the summer time, AP will average around 190 WH/m, and I can get 160-170 WH/m. As mentioned previously, the AP doesn’t use regen enough. My route includes some downhill areas, that I can coast with regen, whereas AP uses brakes.
AlanSubie4Life
Efficiency Obsessed Member
Yep, no surprises here. How do you know TACC is using the brakes? Small difference but there and particular types of driving might bring it out a bit more. Still, really really hard to measure small differences like this. I’d expect less than a 20Wh/mi difference with conservative driving with the same speed profile.
