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Rated Miles, Projected Miles, and Actual Miles

We took a drive yesterday from Seattle to Bellingham and back. The display showed 230 rated miles when we left, and 30 rated miles when we returned. The projected miles jumped around some, but because I was driving conservatively, projected miles generally tracked within about five miles of rated miles. In any event, I returned with about 30 projected miles left also. However, the odometer showed that we had traveled 180 miles, not 200 miles. So what do people use to determine how many "actual" miles they may have left? Clearly both the rated and the projected numbers were overly optimistic.

How fast was your "conservative" driving? Did you have anything else on like heat? What was the outside temp.? Battery range is affected by many different various things.

The problem is they can't predict how you are going to drive and whether you are going on surface roads or the interstate. Driving my LEAF, I find % interstate makes the largest difference. I don't pay much attention to the computed range -- instead, I know that the way I drive, each bar of capacity is about 8 miles on surface roads and 4 miles of 80mph interstate driving, and compute it myself.

@Bsbomber,

I'm not complaining about the range I got (I was driving under 60 and got reasonably good range). I'm just pointing out that you can't rely on either rated miles or projected miles to predict how far you will get. I might prefer to have a raw number such as "state of charge percentage," rather than a derived number such as rated miles or projected miles. I guess you could consider rated miles to be a reasonable surrogate for state of charge percentage.

As @jat mentioned, I too drive a Leaf and you start to understand your range depending on how you're driving, hills, freeway, surface streets, AC, etc. I always joke with friends that ask about range anxiety that I find myself driving very conservative to my destination and "who cares, I'll make it home" when I'm driving home!. The Leaf has a much more limited range than the Tesla (and its for the wife) but eventually you figure it out. Regardless, driving without gas, heat and noise is simply the best.

My (wife's) Tesla arrives very, very soon...

Rod and Barbara have tried a systematic approach to understand what's up with all these different kinds of miles:
http://www.teslamotors.com/forum/forums/rated-miles-and-predicted-miles

Battery Percentage is A MUST feature

@DouglasR Sorry for the off-topic questions but I live in Vancouver, BC and am interested in the Model X. Which battery version do you have on your S and did you have the heat/radio on for your trip? I'm hoping the 60kW Model X can make it from Vancouver to Seattle on a single charge in any conditions and without having to conserve energy.

Thanks.

@stoked, I drove slowly (60 mph or less), and the car is configured for "range driving mode" (i.e., the fan is somewhat restricted and seat heaters are used more). However, I also had the sound system going, it was raining quite a bit so the wipers and blower were on, and the cabin was kept comfortably warm. I have the 85 kWh battery, but remember: I went to Bellingham and back on a single standard charge -- i.e., not a range charge. You should have no problem getting from Vancouver to Seattle in a 60 kWh car, but I would think about getting supercharger support for added flexibility.

@stoked - note that the Model X is going to use more power to cover the same distance because it has higher CdA and weight. I don't think they will know for sure yet, but I think the estimates were around 260mi range rather than 300, so I would expect an EPA range for the 85kWh battery at more like 230mi.

Of course, battery technology may have improved enough by then that speculating now is a waste of time.

@DouglasR Thanks for the details. Hopefully the 60kWh X has somewhat close range to the 60kWh S.

@jat@jaet.org I figured as much, I guess I'll have to wait to see what the range is for the 60kWh X.

I too am not sure of the actual range I can drive. I drove 82 miles today on a standard charge (started out at 238) which should leave 156 but I ended up with 120. So running the heat, radio, etc.. took 36 miles of range? Seems like a lot.

I have had my car a week. It has surpassed all my expectations but if I had to say one thing, it would be that I am surprised at how much mileage the heat, radio, or whatever else uses the power takes from the projected mileage. So even though in the morning it says 238, in reality, it may be truly only 160 miles. Just glad I got the 85KWh battery.

It is the nicest car I have ever had and I truly enjoy it!

@lgagliard - the speed you drive also matters a lot -- the 300mi range is based on constant 55mph. The EPA figure is based on a mix of driving, so if you drive nothing but interstate at 75mph you will get less.

Speed has by far the biggest effect on range. Everything else is secondary. If you think you can't make the distance, slow down. Range sweet spot is around 25mph.

BTW - wouldn't simpler nomenclature help reduce confusion?

Actual, Projected Range ===> Range

Rated Range ===> Max

I know the current terms are born of layers of engineering subtlety, but most consumers need a more common sense handle for what these numbers mean to them.

I think "Range" and "Max" convey it more simply.

Software updates are a beautiful thing.

Rated range is not max range. You can go quite a lot further than that. Similarly Projected range doesn't match actual range, it is estimation based on your driving behavior that far.

IMO you should not have "rated range" in display at all, it just confuses people. Just projected one (maybe change word "projected" to "estimated").

The new software update is not good. It is much more important to know your projected range based on your driving habits than some imaginary number which may or may not bear any resemblance to what you actually get.

The Rated Range provides a standard, a measure to tell you how much you could get if you're prepared to drive "by the book". I'm sure that's how most drivers would view it, and why it's valuable.

As I understand it, Rated Range uses EPA's new 5-cycle standard, and is based strictly on the State of Charge, i.e., independent of your driving style (when Rated Range drops to 0, SoC is greater than 0, however). Rated Range after a full range charge should be about 265 miles in mild weather.

There is a new setting called Ideal Range, which I cannot seem to get my car to display. This measure uses a hypothetical driving style more conservative than the EPA standard, a steady 55 mph on a level surface with no climate controls or other accessories running. Ideal Range after a full charge should be about 300 miles in mild weather. Again, this measure is independent of your actual driving style.

You can choose to have either Rated Range or Ideal Range display on the instrument panel under the speedometer (this is my understanding; I cannot seem to get Ideal Range to display). Projected Range, by contrast, displays on the right-hand side of the graph on the Energy app. Projected Range does depend on your actual driving style, and you can choose to have it computed based on your last 30 miles, 5 miles, or 0.1 miles of driving.

None of these measures, of course, is guaranteed to correspond with your actual range, as determined by your odometer. I find it useful to monitor Projected Range while on a long trip. It provides the feedback I need to modify my driving style in order to achieve the range I will need to reach my next charging opportunity. So, for example, on a recent drive I was able to keep Projected Range within about 5 miles (+ or -) of Rated Range.

What I think would be most useful would be an app that takes into account all of the relevant variables: outside temperature, road type and terrain on the planned route, number of people in the car, etc. (think of combining the tools found on http://www.teslamotors.com/goelectric#range with those found on http://www.jurassictest.ch/GR/). The idea would be to plot a course that gives you a fairly accurate estimate of how much energy will be required to reach your destination, and then to modify the controllable variables (speed, accessory use) to match that estimate on a continuous basis. Maybe as I get more accustomed to driving this car, I will internalize these calculations, and they will become second nature. But until then, I think the more information, the better.

I was in a Tesla store yesterday having a very similar discussion with the Asst. Mgr. As a fair amount of the driving we do is in the mountains/foothills, I would be more than happy to enter my destination into the Nav system, even if I knew how to get there, if the Nav system would look at the route and elevation changes and calculate projected energy usage and then compare that to what is available, etc.

Without having paid too much attention to it, in my daily commute of +/- 60 miles I'm using up closer to 80 rated miles.

Two points:

First, I called Ownership, and finally learned how to set Ideal Range to display: it can be found in Controls/Settings/Units & Format. I guess I could have found it if I had searched the Owners Guide for "ideal."

Second, according to the TM rep, and contrary to what I stated above, there is in fact some relationship between actual driving style and Rated Range. I could not get a clear answer as to how that is different from Projected Range, and frankly, it does not make sense to me. The solid horizontal line on the Energy app displays something under 300 Watt-hours per mile for the Ideal Range rate and something over 300 Watt-hours per mile for Rated Range rate. I have not seen any change in the Rated line in the week I have had the car. I'm wondering: do others have this line at a different level, and have you seen it change over time? In any event, until I get some clarification on this issue, I cannot stand by my earlier assertion that Rated Range is unrelated to actual driving style.

Where does the rubber hit the road? You want to know how much you need to "restrain" your fun-driving to reach your destination. Comparing projected to Rated or Ideal helps you do that. What's the problem?

I see the problem as ideal or rated are both useless facts that do not actually tell you what to do.

I would like to see car give you actual real time usage as number and tell you how much power you should be using to get that usage in power meter. Maybe even show you your desired range from navigation info and how much power you can use to get there. IOW "don't go above this line and you are safe" -info.

Something like:

340Wh/mile or less needed
360Wh/mile current usage !!!

(both numbers change as you go, power usage or energy usage both work)

Maybe even with programmable safety margin (choose between 5-20% battery state)

+1 Timo
The car can warn you that your current energy usage exceeds the usage to reach your destination

While I have also found this confusing - and the small dashboard display is so small - I think they'll get it sorted out. My understanding - I'd love to be corected:

Rated range: Driving the EPA way
Projected range: How far you can go driving the way you have been for the last (SELECT ONE) 5, 15, or 30 miles
Ideal range: The "max" range you could possibly squeeze out.

None are precise. If you are driving from Tahoe to Sacramento, you could get more by going 55 and regenerating like crazy.

I am hoping that in the next several months we'll get a better explanation.

Richard

rzitrin;
+1

@ DouglasR, et. al. – If a Tesla rep told you Rated Range is related to the way you drive, the rep was wrong (unless he meant the rate at which you use up Rated Range is related to the way you drive). Your 12/18/12 description was correct.

Rated Range is based on the EPA’s 5-cycle test. So after a Max Range charge with a nominal battery (note that most people will have a above or below nominal battery) will result in 265 miles of Rated Range. The power usage of a Rated Range mile is approximately 307 Wh/Mile (empirically determined value from my test data) and does not change based on your driving style. It is correct to say that the Rated Range miles and battery SOC are linearly related and in a perfect world (car) any SOC value would always display the exact same Rated Range miles. However, the SOC and Rated Range values appear to be calculated using independent algorithms so their linear correlation isn’t always precise.

The new setting called Ideal Range is based on driving 55 MPH on a flat road. It should behave exactly like Rated Range, just based on a different power usage. I don’t have enough data to say what the Ideal Range miles for Max Range and power usage are, but my guess is that they are about 300 miles and 270 Wh/Mile.

Predicted Range is displayed on the Energy app and is computed based on recent driving experience. 30 miles, 15 miles, 5 miles, or 0.1 miles can be selected as the recent driving experience distance for calculation. Each time the car is shut down this selection defaults to the 0.1 miles selection.

The advantage of Rated Range and Ideal Range is that they are predictable and constant, not affected by your driving conditions, and therefore always provide a reliable estimate of the useful battery capacity remaining in the car.

Lets return to your original question concerning the round trip between Seattle and Bellingham where you drove 180 miles but used 200 Rated Range miles. If your Projected Range and Rated Range had matched precisely throughout the trip, then your distance traveled should have matched precisely the Rated Miles used. You said the Projected Range and Rated Range matched within 5 miles plus or minus throughout the trip. Since Projected Range is only based on recent driving experience it may agree closely with Rated Range at some point in the drive and hide the fact that the driving experience older than the selected Projected Range was worse than the Rated Range standard. One method to try is to reset one of the trip odometers when you begin a trip and note the Rated Range. Monitor the Wh/Mile on the trip odometer – if it is below 307 Wh/Mile you will do better than the original Rated Range value, if it is higher than 307 Wh/Mile you will do worse than the original Rated Range value.

You asked, “what do people use to determine how many ‘actual’ miles they may have left?” I don’t think there is any single gold-standard formula. If you are familiar with your driving style and the route ahead you will have a good feel for whether Rated Range will be right on, pessimistic by x% or optimistic by y%. If you know the route ahead will be fairly constant and you will use a consistent driving style, then Predicted Range should give you a good answer. If there are lots of unknowns then you need to build in an appropriate fudge factor and if things get tight, slow down.

Thanks, Rod and Barbara. That explanation makes perfect sense to me. And yes, you are right that on my trip, I probably started out with my energy consumption fairly high, but then drove more conservatively when I realized that I needed to stretch out those electrons. I was probably keeping Projected Range close to Rated Range only for the second half of the trip out and for the whole way back, but lost those 20 miles during the first part of the journey. That was easy to forget, since Projected Range covers only a 30-mile average. However, it is good to know that Projected Range will equal actual range for the REMAINDER of the trip if I am able to match Projected and Rated Range for that segment. After all, what matters is not how far I've gone, but how far I need to go to reach a charging outlet.

One person did comment, however (in a different thread), that the line on the Energy app graph representing Rated consumption changes as he drives. I agree with you that it does NOT appear to change, and 307 watt-hours per mile is just about where it appears to be (hard to tell because the x-axis does not show fine gradations). Now I'm thinking he misunderstood, and was actually saying that rate at which he uses up Rated Range depends on his driving. I will find his statement and report it back here, but I would be interest whether anyone else thinks that this rate varies.

Ok, the comment was by Klaus in this thread: http://www.teslamotors.com/forum/forums/full-300-mile-recharge-issue

And he did expressly reference the flat line on the Energy app graph. I will pursue this further, but not right now. Dinner calls.

Yes, both Rated and Ideal are standards that you can reference and "compete" with, on brief stretches or the whole trip. Your predicted actual mileage will be your own SWAG from observing the difference -- whether better or worse.


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