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A show-stopper for my eventual Tesla ownership...

I've followed Tesla from its early days when the Roadster was first introduced.
My enthusiasm has been steadily solidified.
I was 110% absolute that the model S Performance will be my next car.
...That is until I was "driving home" after a "beautiful" test drive a model S Performance few weekend ago.

Here are my 2 problems:

1. Show-stopper: Tesla cars are not able to "coast".
Letting off you accelerator and Tesla car "actively" slows you down.
In normal driving, both stop-and-go city traffic and highway driving, as a "green" driver, I "coast" my car quite often.
I even coast when temporarily breaking out of cruise control.
In my test drive, from the ram I merged into the fast highway. I got the Tesla to 100 mph in a blink (LOVE IT!!!) and without knowing it. Once I realized that high speed, as usual my foot was immediately off the accelerator.
I expected the car's momentum will gradually, steadily, and safely slow down to desired speed, i.e. 75 mph.
Tesla car "actively" slowed down significantly.
This is very dangerous as my Tesla would be slowing down and obstruct the vehicle behind me.
It thus required me to constantly pressing my accelerator to control the precise deceleration.

2. Another lesser but still is a show-stopper: Brake-lights are on...but I didn't even brake.
I supposed this is the programmed brake-light-on by Tesla's own implementation.
Due to its "actively" slowing down when foot-off-accelerator, Tesla turns brake lights on to warn folks behind us.
Though this is only a "visual indicator" and not as critical as the "not-able-to-coast" problem above, it bothers the heck out of me. It annoys me quite a bit when folks apply brake for no real safe-driving reason, especially on the highway.

Obviously I had a GREAT test drive.
I'm still crazily IN LOVE with Tesla.
I'm so PROUD that TESLA was invented and manufactured in the USA.
I even equate Elon Musk to Henry Ford for his innovations.
But I'll confess that unless I'm completely wrong on the above 2 issues or Tesla will correct them, I'll find myself not a Tesla owner :-(

Those who own a Tesla, please, please...prove me wrong! I'll appreciate you so much!

@ goneskiian, the older I get the more typos I make. :P

Interesting point...I was under the impression that ALL test drive cars were limited to 80. Let's see if npham1212 responds before assuming troll-ishness, but it is suspicious...

FWIW, my test drive vehicle was not yet limited. The Tesla store had just received it that week and no one had yet turned on the limit.

Even with regen enabled if you want to "coast" just let up on the accelerator. If you keep it just a bit depressed, the energy use falls to a trickle so the motor is substantially coasting and the regen doesn't activate. Even when you coast in an ICE car there is still some fuel going to the engine to keep it running.

@ goneskiian | JUNE 21, 2013: One point of contention in this thread though, they are BRAKES not BREAKS!

Yes, please spell this correctly. I have seen it misspelled (in this and other threads) so many times that it's starting to look normal.

@npham1212: You can correct the spelling of your post by hovering over the Tesla logo and selecting edit. Older folks, like me, will be much happier and your post will be taken seriously.

Yes, as long as you are over 20 mph cruise control will manage both accel and regen to maintain speed.

What everyone is saying is that the MS reprograms your wetware (brain) to get the most out of its capabilities. You may be more resistant than most to the process, but a week or two is likely to change your POV.

I'm reading in earnest, and in unbiased discovery mode.
Well, actually a tad of lifetime-ICE-driving habit bias ;-)

a. A Tesla manager accompanied me on my test drive. He was great! He must have forgotten to point out the "low regen". I'll sure test drive again with "low regen". However, I'm in absolute agreement with @AmpedRealtor in "Remember that from an efficiency standpoint, it's less costly to let the car coast a greater distance than it is to use regen to slow the car down in order to put a charge back into the battery."

b. @prytog – my test drive was on 06/08. Apparently no such restriction of 80 mph was introduced. I was aware of Tesla super acceleration. Of course I wanted to feel that. I did not intend to reach 100 mph, but it came so effortless in a matter of seconds. The Tesla manager proudly confirmed to my friends in the back seats that I hit 100 mph. I travel by car on average 25K a year, and never reached 100 mph in the USA, automobile or motorcycle. I did drive +100 mph when traveled in England though ;-)

c. On comments similar to "...crush the brakes all the time in an ICE": Actually, my driving practice (both city and highway) is to gauge both speed and distance to the car in front such that often I don't brake (thank you @goneskiian ;-)) unless absolutely necessary. It's a lifetime green-driving habit that accelerates gradually then releases accelerator to coast without braking. I optimize car's fuel consumption this way. My right foot is normally on gas pedal with near constant pressure or simply off (i.e. no pressure on right foot)

d. My complaint here mainly relates to the comfort of driving: I either apply pressure to maintain speed, or simply apply zero pressure to coast (decelerate). Requiring precise and prolong foot pressure to coast (decelerate) is not comfortable / acceptable to me. Since my Tesla test drive, I began to notice more on the high frequency of coasting my car: downhill, approaching heavier traffic, pick up speed to safely change lane then naturally decelerate, approaching red light, and especially stop-and-go commuting traffic, etc… My right foot was free from any needed pressure on all these instances

e. Unless the next test drive proves otherwise, with the knowledge shared here, I think there are options:
. Use “low regen”. Btw, @LMB, I spoke to Jeff from CA Tesla, and he told me that there are only standard / low regens. Regen can not be turned off
. @AmpedRealtor suggested Can't you just put the car into neutral to coast? Since there is no mechanical gear switching, I guess it is more acceptable. But it would be annoying to constantly switch in/out neutral in a slow commuting-like traffic

Thank you all so much.
I’m hoping to learn more from Tesla owners.

I got the Model S because I hated all the newer cars that coasted. They felt out of control.

You will learn to love the responsiveness and precision. You can adjust the regen to the setting that works best for you.

Buy the car and get used to the regen. Your reflexes will calibrate after some time.

Coasting is only more efficient if you're going downhill for prolonged periods. It's not as efficient when you're on level ground especially when you realize the regenerative braking is putting energy BACK into the battery instead of wasting the energy by heating up the brakes or simply coasting to a stop.


@npham1212 wrote: "However, I'm in absolute agreement with @AmpedRealtor in 'Remember that from an efficiency standpoint, it's less costly to let the car coast a greater distance than it is to use regen to slow the car down in order to put a charge back into the battery.'"

Can @AmpedRealtor or anyone else cite any references to back up this claim, that "coasting" (in neutral?) is always greener than using regen.?

Maybe it's true in a glide test where you never touch the brake, like a Soap Box Derby. Maybe it applies to a Prius that applies most regen when you hit the brakes. But I don't see how it applies to real world driving in a Model S.

The Model S uses regen. to increase energy efficiency. Disabling regen. (by coasting or selecting "low" regen.) therefore must reduce energy efficiency. Coasting in a Model S is really less "green" than slowing down with regen.

Take one example: Start with 100 miles of rated range. If you "coast" a Model S 10 miles down a 5,000' mountain (bypassing regen.), your rated range (aka. battery state of charge) at the bottom of the mountain will still be a little less than when you started the descent, maybe 98 or 99 miles, due to energy used by heater, A/C, lights, displays, computers, cooling fans, radio, etc. One must also assume that your brake pads will also be a little thinner.

However, if you use cruise control and regen. all the way down, chances are high that you never hit the brake, and your rated range at the bottom of the mountain will end up being a little more than when you started, maybe 101 or 102 miles, thanks to kinetic energy being converted into electricity. Some of that electricity will power the cabin accessories during the 10 mile descent, and most of the rest will be stored in the battery.

So, the regen. car hits the flats with 101 or 102 miles of rated range. The coster's car hits the flats with 98 or 99 miles of rated range. Do you think the coaster could safely coast "a greater distance" (2-4 more miles) on the level ground at that point? I don't think so.

Coasting is definitely more efficient than regen if you are coasting to a stop. But this requires constant monitoring of stopping distances. You are trading the minor physical effort required to keep your foot on the accelerator in order to coast by using partial pressure vs. perpetual vigilance and mental calculation to coast to a stop. Furthermore, this is only effective when traffic is minimal or very predictable. I suspect that your intolerance of brake lights is due to your dependence on knowing what your stopping distance is going to be. I imagine that the occasional car cutting you off must send you into hissy fits.

Also, I can imagine that being the car behind someone doing this is going to be EXTREMELY ANNOYING. I imagine that if you are driving along at 40mph (let alone 70) and want to come to a stop at the next intersection, your coasting method would require you to let off the accelerator long before the actual stopping point thereby forcing all other cars behind you to also reduce their speeds.

I agree that with constant vigilance and tolerance to annoying everyone on the road AND an environment with predictable traffic, coasting to a stop is more effective than the regen on the Model S. However, I don't think most of us want to spend our time driving constant making mental calculations as to when we want to stop and how long it would take to coast there, nor do we want to be stuck behind someone doing this.

"Ultimately get farther on less energy by coasting than by using regen."

I think that is bunk.
I leave my house with, say, 235 projected miles.
I drive the 10 miles to Boulder, CO, 1800 feet lower,
and I still have 235 projected miles. Sometimes 236.

No way is coasting going to give you ten free miles. And it breaks the brakes. ;)

And low regen? Waste of time and energy. Not to be too rude about it, why
do you want this modern vehicle to feel as though it has an old fashioned automatic transmission? Drive it and you'll learn to love it.

Your calculation of the car having 101 or 102 miles left assumes that you stop the test at the bottom of the hill. If you let the cars continue, you'll find that the car that coasted will be several miles down the road whereas the car that regenned will not have gotten as far on the same energy. Regen is not 100% effective. In order to do a proper analysis would require a lot more information, but all else being equal, not matter how efficient the regen is, coasting a car without using any brakes at all is more efficient than having the same car alternate between using and regenning electricity.

That said, without careful planning and a very predictable environment, this is not practical. In the real world, there will be times when you are forced to slow the car for traffic, curves, pedestrians, etc. that will negate the advantages of coasting.

But the OP is correct that in specific situations, coasting is more energy efficient than regen.

I love the regen and other than my test drive have never driven the Model S on low. And you are correct OP, it cannot be turned off. The Model S, and I assume the Roadster as well, is a different style of driving that took me about 2 hours to become accustomed to. IMO the only efficiency to be gained by coasting is going down a hill that will be immediately followed by a short uphill so that you can gain speed to get over the hill without using any juice (in neutral).

Regen lets me corner without using brakes (and gaining energy!). Mountain switchback driving feels like a manual transmission without the nasty clutch/brake smells. The brake lights don't come on at low regen levels, but I do agree that it's regretfully an annoyance for following drivers, but think it's the safest way to go. Once you're used to driving, this will smooth out and be less of an issue.

Someone correct me if I'm wrong please, but I think the lower brake lights come on with regen, but the rear window light is added when the "real" brakes are used.

My advice is, if you're not feeling comfortable with this reassurance, take some more test drives, see if you get used to it, and if it's a deal breaker (or deal braker?) then, unfortunately, so be it.

@HenryT2 wrote: Your calculation of the car having 101 or 102 miles left assumes that you stop the test at the bottom of the hill. If you let the cars continue, you'll find that the car that coasted will be several miles down the road whereas the car that regenned will not have gotten as far on the same energy.

I don't understand that conclusion. I guess it would be true of soapboax cars (no brakes), but this was attempting to be real world example, where both Model S cars are required to obey some real world speed limit during the downhill run, say 70 mph max.

The coaster would have to use the brakes at some point, wasting energy. Even if never used (shallow slope), the coaster would end up with less energy in the battery at the bottom of the hill, because they are using no regen.

When they get to the bottom (at about the same time), the coaster will have about 98 miles of range left, and the other will have 102. Then they get to drive until empty, over flat ground. The regen. driver will be the clear winner.

Getting back to the OP, there is no reason whatsoever to think of the aggressive regen. as a show stopper. It in fact is a wonderful feature, especially when going around curves.

And is actually dangerous to put your car in neutral and coast downhill, because sometimes you need to accelerate suddenly to avoid an accident, and if you're in neutral, you can't. This is probably why it is illegal in California (and other states I assume):

From CA Vehicle Code:

Coasting Prohibited

21710. The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such vehicle in neutral.

Well, if you are at all like me and grew up on a manual transition and downshifted to either slow or gain optimal gearing and torque for turn entry/exit, then this car was designed for you once you adjust. For the past 8-10 years, I have been constantly using paddle shifters in a 5 series or e class to gain the same effect. The Model S allows you to archive that with one foot and minimal effort via small adjustments. Question for the OP-have you driven the Model S in stop and go traffic? OMG- it is a game changer. Total control with the right foot. No more brake-accelerate-brake-brake harder-accelerate-brake again BS. The simplicity and ease of throttle-based speed control takes all the stress out of it. Stay open minded and schedule additional test drives. Tesla reps will take care of you. I took 5 test drives before I committed - early adopter with massive late majority tendencies :-). Good luck and I hope you make the move to the Model S. There really is no going back. Just sayin.

Regen is one of my favorite features. I rarely use my brakes in normal driving. It tool me about 1 day to adjust to the strong regen of the car. I guess its not for everyone!

I agree with all who have cited the merits of regen braking, both for safety and efficiency.

We live on a 700' hill and it is straight downhill for 3 miles. We have to drive down a very steep street with a speed limit of 25 mph, through a residential and school area. All of our ICE cars require major braking, even in a low gear, and our brake replacement costs have been high, not to mention the lack of safety. But the Tesla Model S gracefully goes down the hill, under complete speed control and we get down the hill, without losing a single mile of range. This alone makes the Tesla worth every dollar of its price.

I wholeheartedly agree with the regen supporters. It improves the feel & control (close to downshifting in an ICE only better). I'm thinking I may never have to replace my brake pads. I also like the brake lights on deceleration.

Downhill at highway speeds I will regen when I back off on the go pedal. There is no appreciable deceleration and no brake lights when I do this. I've had the car 6 months and I continue to marvel at the engineering.

HenryT2 is totally correct.

By definition, when you convert energy from one form to another there is a loss to inefficiencies in the conversion process itself. No conversion is 100% efficient. I believe the Prius regenerative breaking system is only 33%-50% efficient. So that means 50%-67% of the energy is LOST in the regen process. Your car slows down, you are losing more than half of your energy to conversion inefficiencies compared to simply coasting. For the regen vehicle to catch up to the coasting vehicle will require engaging the battery and using the energy you've stored up from the regen to propel you forward. Remember, however, that energy came at a 50%-67% penalty earlier. Those ions came at a very high cost through conversion inefficiency. The coasting vehicle will go farther in the same amount of time while using less net battery energy. That's the theory, anyway. I don't have the equations, but I got a B in physics so I'm pretty sure I'm somewhere in the ballpark.

The best rule of thumb would seem to be to coast whenever possible on straightaways and downhills, and use regen as needed for braking. In my Prius I can toggle those modes using just the accelerator pedal. This gives me fantastic mileage.

Regen is one of the best features! It lets you get your rocks off without coasting into the car in front of you. you put the car precisely where you want it, without wearing out your brakes. It improves your reaction time and makes you overall a better driver.

Coasting seems barbaric and chancy now after 9 months of ownership. When I take my Prius out for its monthly sympathy drive. I'm always having to back off other people bumpers, or just get used to the increase in reaction time.

You'll never go back after driving the car with the regen on for a few days.

my 2 cents

I was using the Prius as an example, I don't know what the numbers would be for Model S, however Tesla cannot defy the laws of physics and deliver you more net energy after a conversion from one form to another.

@ JohnnyMac
I totally agree - I'm suddenly 15 again, back in the Midwest, learning enough to get my license on the day I turn 16 (did, but my parallel parking almost cost me). In a 1978 Volvo station wagon with the stiffest clutch I've ever come across.

In snowy winters, you do _not_ brake, you downshift to slow down before a stop sign/light or exit. Brakes lead to pileups and/or damage from snowbanks. :-/

Point being, the standard regen is pretty genius in all respects (energy reclamation, normal usage either stop-n-go, around town or freeway). And I do it all with one pedal!
This coming from a pseudo purist that whined when his wife got an '85 vette with automatic transmission.


It's simple physics. If you don't use the brake, it's all electrical energy converted to kinetic energy. When you use regen, you're turning kinetic back to electric and losing some energy in the process. But, this is in ideal conditions.

I'm not saying the OP is correct Regen is the way to go in real world conditions. But the OP seems to be more interested in "playing games" than in actually getting the best drive.

If you drive without ever touching the brakes (as the OP seems to want to do), up a hill, down a hill, flat, fast, slow, etc. you will get more out of the car w/o regen. I see VERY few situations where this would happen. On an empty road with no pedestrians or wildlife maybe??? A race track?

The OP had a second "pet peeve" about brake lights. That says to me that he's the type of guy who likes to drive and coast to a stop. Which means when he's driving 45mph, he's letting off the gas about a quarter mile down the road and just letting the car coast to a stop. This is, in fact, better than letting the regen kick in. But it would annoy the hell out of anyone else on the road. It's also not a very efficient method as it doesn't account for any unexpected obstructions.

By the laws of physics, regen is less effective than coasting when there is no braking. Your example of the hill and 102 vs. 98 miles is wrong in many ways, but it'd take a long series of physics lectures to get the point across. But don't just trust me. Ask anyone who has had any training in physics or engineering.

In conclusion, the OP is wrong in every way in the practical sense, but correct in theory.

I think the OP is the only person who does not appreciate the marvels of regen. @npham, as most others have said, given time, you will hopefully come to love this smart, green feature, especially since you clock 25k mlles/year.

I, too, was once a "coaster". Tried to use my brakes as little as possible and I typically drove SUVs. It probably took the most to get used to, but that was all of maybe a week or two. I love the regen now. I drive about 25k miles a year in LA traffic, one pedal driving is a dream. I only use the brakes when I actually need to stop.

As a former coaster, I would find myself letting off the accelerator way too early and wind up way short of my intended stopping point. You learn. Trust me. It's worth it!

Btw, to those who say coasting is more efficient, I gained 9 miles in rated range when coming back from Big Basin national park which has a very hilly terrain. I was coming downhill.

Could coasting have put the charge back in the battery? Could it have saved my brakes?

Coasting will be more efficient if you have the perfect road. If there are imperfections; corners, steep slopes, dangerous situations, speed limits, etc. Than I presume that the theory loses out to reality.

But there is one more point I would like to bring to this discussion. Tesla has tested this vehicle for years to get the maximum amount of miles from the battery. When coasting would be more efficient, it would be available in the settings menu for sure. (Tesla could claim 300+ miles for range!)

You mention that the high level of regen is dangerous because "Tesla would be slowing down and obstruct the vehicle behind me", and then complain about the brake lights coming on when the car goes into this strong regen. The lights come on precisely to keep this from being a dangerous situation - the lights coming on automatically warn the vehicle behind you.
As with most others on this site, I've found that I quickly come to love driving with the high regen enabled. The one pedal driving becomes second nature and I find myself learning how to stop without touching the brakes until the very end. If you don't like driving in this manner you can set the regen to low, and if you don't like the car slowing down quickly when coming down a steep hill you just back off the accelerator slightly or use cruise control when on a highway. It's actually very easy to get used to, and I find I'm disappointed that my wife's hybrid doesn't have this feature when I drive her car.

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