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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.

I also found that the heater/AC with fan running takes up quite a bit of juice. Just sitting at a stop light, my energy consumption (orange part of the speedometer) in non-zero by a large amount - maybe 2 or 3 KWHr. So, depending on how long I spend in the car, I could be using up precious energy. If I spend 4 hours driving, I could use between 8KWHr and 12KWHr of battery - which would equal between 26 and 39 of rated range (assuming 307 watts/mile). Using the driver's seat heater on the highest setting, 3, does not move the orange dial at all.

Also, has anyone noticed that a standard charge in cold weather does not yield the normal 240 or 241 rated miles? I've noticed that since it's gotten colder in the SF bay area this week that I can get only about 237 rated miles on a standard charge. I hope that when it gets warmer, my standard charge miles go back to around 240.

@dahyte, I've never gotten 240 on a standard charge. I typically get around 233-235. My highest, as I recall, was 237, and my lowest was 231. I'm in Seattle. It's been cool here, but mostly in the mid-30s at night, and mid to upper 40s in the day.

@Douglas, so that makes sense then. There is an external temperature dependency on maximum standard charge. My early experience was consistently 240 or 241 miles when charging at about 65F to 75F in the SF Bay Area. Recently, temps have dropped to between 48F and 53F during charging, and I'm seeing 237 miles range on a standard charge. It's also likely that external temperature has a bearing on our actual range when driving - perhaps the battery does not hold its charge as well in the cold?

@dahtye, I don't know how they determine the Rated Range number that appears on the instrument panel -- i.e., whether the car monitors external temperatures or whether it measures the charge level in kWh rather than in percentage of a full charge. However, the lower number in cold temperatures is certainly consistent with the actual mileage we should expect. Take a look at the little calculator on the Go Electric page: ideal range drops from 301 to 287 when you drop the temperature from 70 to 32, even without turning on the heat.

@Douglas, After rereading my post, I mispoke/typed concerning rated, ideal, and projected range. I normaly, on a standard charge, will see 240 miles rated or 275 miles ideal. These don't seem to change more than 1 or 2 miles, probably dependant on temperature. Here in Florida the overnight lows have gotten in the high 40s. The projected range is the dashed line. That's the one I can ocassionally get below the ideal (solid line) and routinely get below the rated (also solid when selected).

My average wh/mi has been slowly dropping and is currently at 308 for over 3500 miles. My driving habits have definately gotten better and I expect my average to drop below 300 eventually. I still enjoy kicking it up a notch on the freeway, but most of my driving is around town at 35-45 mph.

I have been getting *very* close to rated range here in warm South Florida. I don't think you need anecdotal numbers to figure out the rated rage Wh/mile. I believe it's just 85000 / 265, which works out to around 320.75. Or am I misunderstanding it?

@Klaus, But you agree with me that the solid line on the app, whether set to Rated or Ideal, does not change with your driving style? I know the dotted line -- average watt-hours per mile over 5, 15, or 30 miles -- does change with your driving style. But I'm pretty sure that the solid line is the same for everybody: as Rod & Barbara said, about 270 watt-hours per mile for Ideal and 307 for Rated.

@Ron5, not exactly. The numerator is something less than 85000 because the car is designed to use less than the full capacity of the battery for driving. The last 5% is to protect the battery when it gets low. So if you take 85000 watts times .95 and divide by 300 (range charge), you get 269. Similarly, if you divide by 263 (standard charge) you get 207.

Oops, I got that wrong. First, I meant 307, not 207. And this was referring not to range v. standard charge, but rated v ideal range. Sorry.

@DouglasR, good point regarding the 95%, but I'm talking about rated charge here. So I believe the denominator would be 265 for range charge, not 300. 95% of 85000 is 80,750. 80,750 divided by 265 is almost 305. So to me that means I need to average 305 Wh/mi to match the rated miles for a range charge.

Cooler air is denser and harder to push out of the way. Like driving up the Cd a bit in its effect or moving to a lower altitude.

@Douglas, agreed.

It would be nice to have a customizable "Personal Miles" display that would be just a simple Rated Miles number with a fudge factor that each driver can input. If you are an aggressive driver then you could put 0.7 as your multiplier and your Personal Miles display becomes your own special Sport Miles range. If you are an ultra conservative driver then input 1.1 and you get your own custom Hypermiler Miles display.

While I understand that Projected Range/Average should change when you select 5, 15, or 30 miles, I just noticed that Projected Range/Instantaneous also changes when you select each of these three distances. That leads me to think I have been misunderstanding the Instantaneous tab. I thought it was an average over 0.1 miles, but that would be inconsistent with being able to choose 5, 15, and 30 miles.

So can anyone give a cogent explanation of what the "Instantaneous" tab is measuring?

"Personal miles" is a good idea, but no need for a "fudge factor". It's much easier to just be able to input your usual Wh/mile number. So if you usually do around 405Wh/mile, input that and the "Personal miles" should indicate ~200 miles from a range charge or ~175 miles from a standard charge.

This is from.........

Klaus | DECEMBER 22, 2012
@Douglas, After rereading my post, I mispoke/typed concerning rated, ideal, and projected range. I normaly, on a standard charge, will see 240 miles rated or 275 miles ideal. These don't seem to change more than 1 or 2 miles, probably dependant on temperature. Here in Florida the overnight lows have gotten in the high 40s. The projected range is the dashed line. That's the one I can ocassionally get below the ideal (solid line) and routinely get below the rated (also solid when selected).

My average wh/mi has been slowly dropping and is currently at 308 for over 3500 miles. My driving habits have definately gotten better and I expect my average to drop below 300 eventually. I still enjoy kicking it up a notch on the freeway, but most of my driving is around town at 35-45 mph.

So far in the 1 1/2 days that I've had the car, my experience is very similar to what Klaus has experience. However, I am in Illinois and the temperature has ranged between 25° and 36°. I am getting a standard charge that shows rated miles well below the ideal miles but I have only been paying attention to the ideal miles which are around 277 ideal miles. I have been practicing my drive that is coming up tomorrow and hope that I can make it round-trip 165 miles in the cold temperatures. The car will sit out for about six hours at my destination. I am going to be really wimpy and just drive 55 mph or 57 mph mostly on cruise control. However, I also find that it is best to disengage the cruise control when going downhill because there is some regeneration that occurs. Otherwise, it just cuts back on the kilowatts use.

Just to clarify in the above, My comment starts after the dotted line in the middle of the post. I just want to know what other people are experiencing. This kind of information could be really useful to me and I hope other people could benefit from it as well. We can make this private if you want, just let me know.

I'm not talking about software, I'm talking about real practical experience from those people who have driven the car under various conditions.

In my experience you will see more energy use on a cold day to warm the battery & the cabin at the start of each leg of your journey. Your "rated miles" will actually increase once the battery is warmed. Your rated miles should be a good estimate for you once your battery is warmed. Your rated miles when you park the car for 6 hours should help to reassure you for the trip back. If you have concerns you could always plug in to a 120 outlet to keep the battery warm during the day--but I don't think you will find it necessary.


You should be OK, but to be on the safe side, why don't you do a range charge the night before, and set your amperage so that the car finishes charging just at the time you want to leave. You should have about 270 rated miles (I would ignore "ideal" miles, because you won't get close to that consumption rate).

Driving slow is also a good idea, at least until you know what kind of consumption you are getting. If, on the way home, you see that you will have many miles to spare, then you can speed up. Remember, you can use fewer miles if you turn off climate control and use the seat warmers instead.

I would also use Recargo or one of the other sites/apps to scope out where you can stop to pick up a charge if you get into trouble. Of course it would be much better if you could plug in during the six hours you will be at your destination.

The Go Electric page on this site shows that an 85 kWh battery can go 233 highway miles or 211 city miles at 60 mph, with temperatures of 32 degrees, using the heater. It does not take account of your six hours sitting in the cold, which could cost you another 10-15 miles. So you should make it no problem. But it never hurts to plan ahead, and to have a backup in case things don't work out as planned.

The standing loss should not be too bad since it will be in the 30's tomorrow. I have found that if you can warm the battery by charging, even at a low rate, it significantly improves your mileage for the first 15-20 miles, maybe more. Remember to take your charging cable with you. let us know what happens

Douglas and David

It's really funny how anxious I am but I really can't imagine any problems. I am charging at just 10 amps so its completed close to departure. I've been driving a hybrid for years and play the mileage game for fun but this will be a new game with different rules. Even checked winds forecast for the drive. I will plug in the 110 at the office once I can get a close enough spot. They usually open up in the first 1-2 hours. That will help. Unfortunately there are few plug share and charger spots but I have already made contact with a Tesla owner 30 miles from my home but 11 miles off the route. They have a 1450. There is a Chargepoint 5 miles from the office so I will have an idea of how it looks before I return and could always blog the forum from there!

I want to make it with ideal miles and standard charge because this is a regular commute and I don't want to degrade the batteries by doing a max charge 3-4 times a week. I will see how it looks before I go in the morning and have a little flexibility to add charge.

Thanks for all your input and I will follow up tomorrow.

Here's my .02,
I break it down like this. I see you've figured out the difference between rated and ideal. What it comes down to is Wh/mi...
Ideal is roughly 285 Wh/mi
Rated is roughly 320 Wh/mi
So after some time you'll fall into your own personal usage. You'll see this happening in the trips page. My avg Wh/mi is 308 for the last 500 miles. So I typically beat the rated, but not the ideal. That will give you the gauge you need to base your own mileage. If you're higher than 320, you'll slip behind the rated displayed on the dash and 'use' more than you cover.
I keep the trips page up on the dash and each time you unplug you have a new average started for that trip, plus you'll have your previous mileage history to go by if you do the same trip over, like driving to work everyday.
When I first got my car, I was up around 320 Wh/mi. But now that its warming up and I use the heaters less and the batteries are staying warm, I have been closing in on 300.
Each driver, car, conditions are different. This is the only way I see to gauge you own mileage and compare against rated so you can calculate total distance.

Rated is at 308 Wh/mile. Projected in the energy app is based on prior 5/15/30 mile average. For road trips, travelling around 70-72 mph, I use 345 Wh/mile for budgeting in moderate weather (10-15% more if really hot or cold). Also need to remember that if you leave it sitting, you lose 12-15 miles/day (again, if not too cold). No easy answer. I've been putting together tools/charts at - will have an energy estimator that accounts for actual route, speed, weather soon.


I agree with cliff that Rated is around 308 w-h/m, and Ideal is around 270. But I agree with you that the Trip display is the most useful tool for combatting range anxiety, particularly the average w-h/m since the last charge. If I can keep it around 305-310, my Projected miles tracks my Rated miles almost exactly.

@drp - I would not recommend a range charge every day, but for your first day, it won't hurt, and you will get a much better idea of your consumption.

I was using 85000 (85kW) divided by 320 (rated) and 285 (ideal) Wh/mi to come up with the 265 mile and 300 mile range respectively.
While that is engineering numbers on paper, I agree with you that around 308 Wh/mi seems to line up right. That's what my average has been lately and I'm nailing the rated mileage as I drive. I'm thinking that's because it factors in drains while sitting and other parasitic losses. The trips only accounts for MOVING averages.
While doing one of my personal tests, doing the daily work commute, I was determined to see if I could hit the Ideal Wh/mi mark. I hit it at 285Wh/mi for 100 miles, two trips to work and back without recharging, by skirting the freeway using 50mph side roads. While I was driving at an Ideal pace, my range was lining up with Rated due to overnight loses, and me pre-heating the car via the app before I drove in the morning. I lost 9 miles over night and used another 3 miles heating the car up each day. Still, in the end I was hitting my rated range. I covered 100 miles, using 100 miles, but driving far more efficiently.
But that's the big picture. Did that just get muddier?

Sounds like the car is training you well ... ;)

@ CnJsSigP - The 85 kWh Battery does not have 85 kWh available to drive the car. That's why 85000 Wh / 265 Rated Miles produces the incorrect Wh/M for a Rated Mile. Based on empirical data I've collected with my S, the usable Battery capacity is about 81.4 kWh and a Rated Mile efficiency is about 307 Wh/M.

I know the difference between theoretical and realistic numbers. Its the world I live in. I see R&B are way ahead of me. I'm slowly coming to the same conclusion. I find this aspect of the S so much fun to drive. Crazy? I love seeing what I can and can't make the car do. So far I'd have to say its done everything as advertised. I am impressed. I've gotten to the point that I'm a bit more carefree on the freeway because I lost the anxiety thru confidence. I want people to see my S keeping up with the pace of traffic. Not having to drive slow to make the range. That's how I sell S's... in fact I think I just heard a Porsche owner trade his carrera in...


Regarding whether the Trips display accounts only for MOVING averages: You are right that, while the car is stationary after a charge, the display shows 0 miles and 0 kWh consumed, even if the car has lost several miles from sitting overnight. However, I think that the over night energy consumption is accounted for immediately after you start driving. I will need to check this the next time I drive, but in my experience, the "average" consumption is extremely high for the first few miles, and gradually drops to more reasonable levels. My display often shows 800+ w-h/m for the first few minutes of driving, even though my initial driving is downhill. I think that the overnight consumption must be dropped into the equation a minute or two after I begin driving.

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