Still confused about Rated Range

Still confused about Rated Range

I've been reading a few of the threads and am still confused about what Rated Range is supposed to show and what I'm seeing.

Yesterday I left a Supercharger with a rated range of 201. My understanding is that rated range is using a simple 308 wh/mi calculation so assuming I drive exactly 308 wh/mi I should be able to achieve the 201 miles my range is showing me.

It just so happened that as I got close to home my wh/mi was at 308 (it bumped up to 309 in the garage) on the line that said "Since Last Charge". I had driven 135 miles from the supercharger (again measured on the Since Last Charge) however my range was showing only 51 miles left. So essentially if I add the two up I would have 186 miles or I lost 16 miles of range despite going exactly the rated range as an average for the trip. We did not make any stops between leaving the supercharger and getting home.

Can somebody explain to me what is going on here? It doesn't even make sense that the formula dropped to 300 for the rated range as that would simply mean that I used another 1,080 watts for the trip (8*135) and I wouldn't use up 15 miles for 1kWh.

Are other people seeing this? Do I need to take it in to be checked? I see this to a smaller scale all the time for my regular drive where my driven miles plus range remaining has lost a few miles from my initial rated range. Thanks.

sule | July 7, 2014

At least one software version I had used some 176Wh/km (283 Wh/mi) for these calculations. That would match your data fairly well - your 135 actual miles would have used about 147 miles of rated range at 309 Wh/mi.

hamer | July 7, 2014

There is a detailed explanation of rated range on Tesla's web site. There are various estimates that many people have given for watt hours per mile to achieve rated range. I have not seen anyone claim as much as 308 can achieve rated range. I suspect it is somewhere around 285 but I have not looked at the charts on lately.

redacted | July 7, 2014

The rated range line on my energy meter runs about 290 wh/mi. I find the last 30 miles, when driving distances at least, is the best way to figure your projected range (on average, not instantaneous).

But I only think about range when I'm going to run out.

ks-man | July 7, 2014

I'll have to check again where my rated range line is. I usually just look at the small graph on my dash rather than the large one on the screen. 285-290 doesn't seem that realistic from my experience. In the summer I've been averaging about 310 and the winter I was around 400. I'd be very surprised if somebody doing normal driving could average under 290. I thought the whole point of rated was a more realistic calculation and ideal range was if you intentionally were trying to get the absolute lowest number possible (which to me would be around 270-280)

This was the thread I saw where everybody spoke of 308.

Anthony J. Parisio | July 7, 2014

Rated range is an ever changing guess. Just like miles per gallon in an ice car, it is only a calculated guess based on driving habits. The difference is m/g is calculated after you have used the gas. Here we are trying to guess before you use the electricity on past use. This makes it an even more inaccurate guess.

You just need to come to know your car. If you travel the same route and do all the same things, what ever you consistently get is what your real range was. Your cars batteries might last for over 15,000 miles before they are down to 60%. Loss of range should be the last of your worries. Just study your results as you drive. Write it down or keep it in your head. You will come to know your range better than that "before the fact guess".

I hope this helped.

sule | July 7, 2014

@ks-man: it changed over time. Since I had the vehicle it has been either 283Wh/mi or 300Wh/mi, depending on the version I has - not 285, not 290, not 308.

sule | July 7, 2014

"I has" -> "I had"

sule | July 7, 2014

One more note - my numbers are about +/-1,

tes-s | July 7, 2014

I believe the rated range calculation is based on estimated usable kWh remaining and a wh/mi constant. I also believe that constant is different based on market and model (60 and 85) - but should remain the same for a given car (except with software updates).

ks-man | July 7, 2014


The issue at hand though is most people don't care about rated range when doing their normal daily drive. I drive 30 miles each way back and forth to work and I know about what I'll average for that trip but truthfully my average doesn't matter. When I'm sitting at a supercharger for a road trip is when I care what my range will be. I thought it saying 201 miles means that I could get 201 miles if I average around 305-310 wh/mi. Now my trip was only 140 miles so I knew I would be fine but the whole purpose of the range is for it to be a gauge for people to use. Not just a random number on the display to confuse people. How can you plan a trip around that? If rated is closer to 280 then again I can use that number and if I expect to average 320 then I know my true range is 12% worse than what the number on the bar is telling me. Also if you look at the thread I quoted a response from a Tesla employee did say that the rated range is based off the car's remaining energy/a fixed wh/m.

For some reason I had 309 in my head as rated for the past few months. I'm sure I read something that was inaccurate. This is an interesting comment from the letter in that other thread "Rated range = the car’s estimate of remaining energy / a fixed whpm. The fixed whpm is different for different vehicles (85kWh / 60kWh) and in different markets based on the regulatory test for that vehicle in that market."
I had never heard that rated is different in different markets. I don't know if that means US vs. Europe or Southern Calif vs. Montana. I'm in the Chicago area and now it does appear mine is in the 280s based on the numbers I've been seeing which seems virtually impossible to achieve and is disappointing that Tesla would put those numbers out there which only stand to make owners trust the numbers provided less. I'd rather see fewer miles on my range but actually achieve those or at least see what wh/m it is claiming I'll be able to achieve so I know how to adjust it. It seems that marketing is trumping usefulness here by restricting this information from the end user.

sule | July 7, 2014

Which version do you have?

redacted | July 7, 2014

@ks-man 290 is realistic depending on how you drive and where you drive. Around town in fair weather I can get 250 wh/mi over a good distance. On the highway at 65 driving East I can hit 290 without difficulty. Going over 65, driving West (into the wind) etc, the number goes up. In winter it seems like presenting the door handles uses 290 wh.

Anyway, the rated range line is right there on the energy graph. It should be straightforward to figure what the value is.

CT-Greg | July 7, 2014

"285-290 doesn't seem that realistic from my experience. In the summer I've been averaging about 310 and the winter I was around 400. I'd be very surprised if somebody doing normal driving could average under 290. I thought the whole point of rated was a more realistic calculation and ideal range was if you intentionally were trying to get the absolute lowest number possible (which to me would be around 270-280)"

I don't know how she does it, but my wife seems to be able to pretty consistently hold it to about 260 while keeping pace with CT highway traffic.

sule | July 7, 2014

@redacted: the constant used for rated range is NOT necessarily matching the line on the energy graph. In fact, when I first upgraded to 5.9 it did not. The energy graph remained at about 186Wh/km (300 Wh/mi) but the rated range calculations used 176Wh/km (283Wh/mi).
One *is* easy to achieve, the other one definitely is possible but is not easy. Newer upgrades got me back to the two being in sync again.

@CT-Greg: I was able to hit these consumptions (even bettet) with a lot of self control, definitely not keeping up with the traffic (unless slipstreaming / drafting). I just can't see myself doing this for the whole trip. I had some people in the car the other day and was tight on range. With mostly highway driving (fast, empty highways), driving at speed limit I got only to "normal" rated range, not the reduced consumption one.

Jonathan D | July 7, 2014

My S60 always has shown 300 Wh/mi as rated. Conservative driving on the freeway (cruise control @ 65, range mode on) for longer trips usually yields 270-280 Wh/mi average over 30 miles, but obviously is impacted by elevation changes.

I've also found to be very helpful and surprisingly accurate.

Anthony J. Parisio | July 7, 2014


For me on a long trip, I just subtract 50 miles from rated range. This is just to play it safe. However, I am rather conservative.

PV_Dave @US-PA | July 7, 2014

For Supercharging trips I make a spreadsheet and estimate my Wh/mile based on expected conditions (weather, terrain, expected speed, etc). Then my spreadsheet tells me for each Supercharger what rated miles I need to drive the expected distance at the expected energy use with a reasonable (40 miles for me) buffer added. I then charge to that figure.

When someone comes out with a good iPhone app to handle all this for me, I'll be happy. Because I don't have time to write one myself. ;-)

Thom EM | July 7, 2014

If you watch the energy app it places a horizontal line at rated consumption and labels it, though a second line for your current average can make it difficult to distinguish it. In any case, when you get those two lines superposed and keep them that way, you should find that you are getting rated range on the trip since last charge.

That said, I sometimes figure that I'm not quite getting rated range out on the highway, but it's difficult to tell using the method above. However, in commuting below 80 kph, I have actually hit Ideal range during the spring when there is no HVAC load.

However, if you are hitting rated range, the consumption average since last charge should tell you definitively what rated consumption is being used for the calculation.

jacobimm | July 7, 2014

I remember reading in Nick Howe's book that rated range is calculated based on 286 wh/m.

Captain_Zap | July 7, 2014

+1 ThomEM

It is easiest if you use the 17" energy graphs to get familiar with range. There will be a line on the screen representing you rated range.

Try out all the different distance settings and compare averages over different terrain and conditions.

NKYTA | July 7, 2014

And bear in mind, SOC is an estimate and this is software, so everything is a bit fuzzy.

1st world Grin problems.

sule | July 7, 2014

@Thom EM, Captain_Zap:

I used to do that... and am doing it again. But do note that *that* method is unreliable depending of software version. The line you are talking about sits at about 176Wh/km = 300Wh/mi. At one point my 5.9.x software used a different constant for rated range display (282 Wh/mi) but kept the line in the "traditional" place. It has, since, come back, but...

How do I know? Because I was still a newby and kept my eyes on it... initially trying 186/187 Wh/km matched both the line on the graph and, when I was driving at that consumption, my rated range decreased by actual distance travelled.

Later, with the first 5.9 update I actually had a 176Wh/km trip (trying my best to lower consumption) to be surprised to have decreased the rated range by, coincidentally, the actual distance travelled. Next update brought this back in line with the graph.

AmpedRealtor | July 7, 2014

I saw this posted over at TMC...

While this is only someone's speculation, it appears to validate some of the numbers being discussed.

Bighorn | July 7, 2014

My observation of averaging 282Wh/m to achieve rated range is corroborated by simple math. If you monitor your kWh usage on the dash, from beginning to end of using a full charge, you'll see approximately 74kWh. If you divide that by the rated mileage of a range charge, which for me averages 262 miles, you get 74kWh/262m=282Wh/m. I noticed that evtripper uses closer to 300Wh per rated mile so their kWh consumption and rated miles start to diverge. Also notable, matching the rated range estimate line on the 30 mile average works out to about 297 Wh/m, which in the end isn't quite good enough. 308 makes no sense and should be banished from your thoughts.

AndyO | July 7, 2014

I'm sure there is a bricking protection for the life of the car and battery. I wonder whether Tesla has stuck to any repeatable zero mile protection. I know they won't admit to it.

Chunky Jr. | July 7, 2014

The few times I have supercharged, I compare the actual miles driven to the rated miles used (to do this, I just take a picture of the dash before/after), then get an idea of what the ratio is for actual/rated. For most legs of my journey this tends to be about 85-90%. So when I supercharge, I take the actual distance, divide by .85, and then add a little bit of slop to be safe. This works pretty well for me. I don't pay much attention to Wh/mi.

It would be nice if the energy gauge on the main "dial" (the one that has speedometer on other side) could have a line on it that shows what represent rated range, and I would know that going above that will reduce rated range, and going below it will increase it. The energy app on big screen or side of dash display doesn't help a ton since it doesn't update instantaneously.

Captain_Zap | July 7, 2014

I thought that they moved some of that margin with the latest firmware update because people were taking the safety margin for granted and not believing that zero miles meant zero. People were getting caught when they didn't plan for a change to adverse conditions.

I thought that accounted for some of the change in range.

On the other hand, I could have been punked.

nickjhowe | July 7, 2014

@Amped - the image is something I put together. :-)

@ks-man - the simplest answer (thanks to massive amounts of testing by @RodandBarbera) is that:

"For an '85 kWh' car, Rate Range is 265 miles at 307 Wh/mile including the 15(ish) mile reserve below zero. This is the line on the energy graph"

If you want to do 265 miles and finish with zero, you need to do 287 Wh/mile. Af this point you'll still have 15-17 miles of range.

To the best of knowledge this is true through software version 5.11


Docrob | July 7, 2014

Captain_zap, I think you are correct and it is truly silly behavior. I think Tesla should have a bit of fun with habitual sub zero drivers. After the 5th time you take the car more than 5 miles "below zero" the car should bring up a message saying "Now on emergency power from 12v battery: Your high voltage battery has become fully exhausted and is now permanently inoperable as a result of repeated abuse, please contact Tesla to discuss purchasing a replacement off warranty" then disable the screens, then 30 seconds later a second message can appear "just kidding...this time".

Rod and Barbara | July 8, 2014

@ ks-man – nickjhowe’s post is correct. To expand on his comments slightly, the issue you discovered arises because Tesla predicts rated range using one efficiency, about 300 Wh/M in software v5.9, but decrements rated range using a different efficiency, about 284 Wh/M in software v5.9. The reasoning behind this mechanization is discussed in depth here:

The bottom line is that to make your miles driven match the rated miles consumed you must drive at about 284 Wh/M. These numbers are specific to a U.S. market, 85 kWh vehicle. Other markets and other kWh vehicles use different specific rated mile efficiencies. Another thing to note is that each time Tesla tweaks the range calculations in the car these values seem to change slightly. In the original EPA 5-cycle software (1.9.17) the predicting and decrementing efficiencies were approximately 306 Wh/M and 287 Wh/M.

NKYTA | July 8, 2014

I've owned the car for quite a while now (over 18 months) and with all the software updates, it can be confusing what's really left in the tank.

I don't stress over it and plan well, but I'd really like an option for "best estimate by the car of what is zero Watts left" so I can select that. But I realize that it is just an estimate, just like the floatie in your ICE's gas tank. ;-)

Bighorn and Samo have a lot of great real-world use numbers for the 85 & 60. I just make it up as I go along.

Two things: I think NKYTA can do better than 284 Wh/m and I'll test that out driving to the Midwest this summer. My latest test drive occupant must have been counting in his head because he said 0-60 was quicker than 4.2.


Dr. Bob Reinke | July 8, 2014

The only driving I use Rated Range for is to alleviate range anxiety for reaching my destination. I use the Nav milage to monitor the remaing milage to destination, and as long as the Rated Range remains greater than the GPS milage, I know we can reach our destination with the built in charge cushion. If the Rated Range starts falling short, I can slow down and reduce the other uses of juice (heat--air--blower--radio--coasting to stops--etc) to increase my remaining range. Never have a range concern and haven't ran out of juice yet.

Brian H | July 10, 2014

Dr. Bob;
Yeah, keeping Rated greater than remaining is foolproof. I challenge all fools to defeat it!

ks-man | July 10, 2014

Thanks all and especially Nick adn Rod/Barbara. Those posts certainly seem to be correct based on what I'm seeing. What threw me off is that the graph line shows rated as 300 Wh/M which I've since confirmed however as Rod posted it does seem that somewhere below that (apparently close to 284) is what I need to drive to have my range deplete by the amount I've driven.

As everybody here also does I give myself a buffer and do have a good idea what I should get and what I need. I'm also conservative and don't expect (hopefully) to come close to 0. At least now I know that if I want to get close to the amount of miles on my range display I need to drive about 284 Wh/M.

Thanks again.

Brian H | July 11, 2014

You mean below 284 Wh/m. The fewer Wh, the more m.

jordanrichard | July 11, 2014

Based on my driving here in CT, generally not going faster than 75 mph on the highway, I get about 10-15% less actual miles than the rated miles.