Tesla in Traffic Big Energy Suck?

Yes. Tesla sucks in bumper to bumper traffic. People told me here too "it's a great city car", we have a different understanding of "city" where I live apparently...

I get +100Wh/hi in traffic as compared to my highway driving.

It all depends on energy consumption. You were using your AC probably, otherwise you wouldn't have used much energy. Remember that the 550Wh value is per mile, if you consume some energy and drive at 0.1mph then of course the Wh per mile will be higher than consuming the same instant energy (W) for a shorter period of time (like driving faster).

The Tesla is great in stop and go traffic, better than any non-EV, HOWEVER, if you're not moving, but still using some electricity (even miniscule amounts) your consumption per mile will be extremely high by definition. This doesn't mean it's using lots of power, only that it's more per mile because you're not going very many miles.

The car will always be better at a constant mid-range speed (I think someone estimated it's best around 30-40mph?) then in stop and go, but that's the same with EVERY car ever built, the difference is that in an ICE it uses a LOT more fuel to sit in traffic then you do in a Tesla, because at least your motor uses nothing unless you're moving.

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Notacarguy said:

But I would have thought that would be offset by the time just spent sitting and not having the car move at all. I was just surprise by the numbers as compared to going at highway speeds.

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Not moving at all is by definition INFINITE energy per mile, as you still use a trickle of energy, even if just for the instrument cluster, divided by zero miles.

Max* said:

Yes. Tesla sucks in bumper to bumper traffic. People told me here too "it's a great city car", we have a different understanding of "city" where I live apparently...

I get +100Wh/hi in traffic as compared to my highway driving.

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does your highway driving include fast moving traffic...tail wind?

I do great in any traffic compared to my normal highway driving where we have no traffic

Right. If there was a kW meter, the kW would be really low. However, the Wh/mi is expected to be high because the divisor (miles) is a very low number. It's simple math.

stopcrazypp said:

Right. If there was a kW meter, the kW would be really low. However, the Wh/mi is expected to be high because the divisor (miles) is a very low number. It's simple math.

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Right. WH/mi is not a good measure of how much energy is being used in heavy traffic. A more useful comparison would be to compare how much percentage of battery charge is used on a given commute in heavy and light traffic (i.e., going this route depletes my battery charge by 12%). You will probably find that the amount of battery charge percentage used on a given route is about the same, regardless of traffic speed. I have found this to be the case in the LEAF. My commute uses about 30% of my battery capacity on a normal day (light traffic); yet, last year, when an ice storm caused this route to take 2 hours instead of the normal 20 minutes, my commute still used about 30% of my capacity.

Zextraterrestrial said:

does your highway driving include fast moving traffic...tail wind?

I do great in any traffic compared to my normal highway driving where we have no traffic

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Over the last 3 months:
Highway driving (lots of random trips), speeding, etc. 260-300wh/mi, where 300 is with speeding.
City (in mixed/heavy traffic) - 320-360wh/mi.

Stop and go traffic is bad for energy economy, but particularly bad for lumbering behemoths.

Energy/mile = ( traction energy + parasitic energy + amenity energy) / mile.
- Traction energy is relatively high because in stop and go you're accelerating and decelerating a lot. While you can recover some energy in regen, at low speeds you aren't going to recover much, if any, and there's no regen on the brake in a Tesla so it'll be 0 if you're using the brake to slow down.
- Parasitic and amenity energy is a function of time, and thus, for a given trip distance, inversely proportional to speed.

Since a large proportion of the load is the traction energy, which is relatively high due to the acceleration, the key to improving is to do a bit of hypermiling:
- If you know you're in stop and go traffic, why are _you_ stopping and going?
- Do you really need to stop and go, or could you roll at a slower, steady speed and keep moving?
- If not, can you accelerate and brake more slowly?

The most expert hypermilers can keep rolling even in heavy traffic. You might not be able to do it, but you can definitely cut down on energy use by keeping acceleration and braking to a minimum.

I've found that if I can find an average speed (even if it's just constantly creeping along at a scant few MPH) that prevents coming to a full stop, my energy consumption during "stop and go" traffic is way less. The worst type of traffic is the type of stop and go where I'm fully stopped one moment, going 40 mph the next, stopped the next, etc. That's a huge energy suck.

Every other car I have owned had a minimum speed it was comfortable with even in first gear, before it would become rough as the speed of the engine reached idle speed or lower so if average traffic speed is slower than that few Mph minimum speed, trying to maintain a constant speed was difficult. In contrast Model S seems to be able to amble along at very low speeds without any drivetrain snatch making hypermiling much easier in heavy traffic situations.

Acceleration and declaration always uses more energy than a constant speed. The Tesla is pretty good about it, but if there are a bunch of erratic drivers sometimes you just can't keep a nice constant speed as you keep getting cut off. It's still nicer to drive in this condition because of the almost one pedal driving, but energy use can go up. On my commute it's between 10 and 20 Wh/mi. Picking one lane and staying in it helps a lot.

What I would say is in heavy traffic, your driving style matters more.

If light traffic = 70 mph and heavy traffic is 30-50 mph, you should do better in traffic. If heavy traffic is 10 mph, you can still do pretty good but your driving needs to be relaxed.

I always do better in traffic. My TACC does better in traffic. But my traffic is not DC traffic.

Another scenario is if light traffic is 60 mph and heavy is 20-40, well - light traffic might win.

Of course accelerating and decelerating uses more energy but usually (for me) the lower speed more than compensates for that. At constant 30 mph I use about 150 w/mi.

The optimal speed is usually around 20 mph but HVAC can bump that. I think the true optimum is 17 but that is why I say "around 20".

David_Cary said:

If light traffic = 70 mph and heavy traffic is 30-50 mph, you should do better in traffic.

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Heavy traffic of 30-50mph? ROOOOOOOFLLLL. OMG, I almost fell out of my chair. Heavy traffic is 0-10mph where I'm at. Full stop and go.

it's not entirely accurate to say that by keeping moving you are using less energy.
If the journey still takes 45 minutes to complete, the AC will still have been running for that amount of time, it will have consumed exactly the same amount of energy.
The only thing that will have changed is that the reporting of the data in wH per mile looks "better"

At least around here, in heavy stop and go traffic you can't use a relaxed driving style because if you let an opening anywhere near a car length appear the driver next to you will cut you off. I'd like the TACC to have a .5 setting for very slow speed to avoid this.

RDoc said:

At least around here, in heavy stop and go traffic you can't use a relaxed driving style because if you let an opening anywhere near a car length appear the driver next to you will cut you off. I'd like the TACC to have a .5 setting for very slow speed to avoid this.

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Same for our area.

I dunno, I always see better wpm in slow traffic than cruising at 75 mph.

The Model S IS better in stop and go traffic compared to an ICE. It all depends what you compare it to...