So I've been reading alot of articles about how people are testing their efficiency in their cars and alot of the time they talk in terms of kwph. As a first time EV owner (soon to be with a MY), can someone dumb down how to better understand how I can tell if my driving is efficient with a Tesla and how to determine range based on that driving by looking at the graphs in the car? Obviously, I'm just used to a gas car where it has a tank gauge and usually a range estimate and I go off of that, but from what I can tell, alot of people go based on battery % or kwph. Sorry if this a dumb post, but I just need to better understand because the numbers people are tossing out are all over the place.
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Efficiency Explained For A 1st Timer
- Thread starter martinb8
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Let me try.. Let's start with a Gas car. Let's say it does 20 miles to the gallon on average. and you have a an 18 Gallon tank. Therefore, on average you should expect a tank to take you for 20 x 18 = 360 miles. Now.. Let say you are towing a boat, or going up a mountain.. by default, the engine has to work harder. which means that it will consume more gas.. therefore, your miles to the gallon will go down let's say to 15 mile to the gallon. in that case, your gas tank will only give you a range of 15 x 18 = 270 miles.. of course there are a lot of factors affecting your MPG.. how fast you drive, how much friction you have (heavier wheels), etc. Of course city driving is less efficient and you can do less because of all the starts and stops.. acceleration takes up a whole lot more energy than steady speed on a highway.
Now... For EVs the concept is the same. The model Y has a 74 killowatt battery. that is 74,000 watts.. So Tesla expects their cars to do 1 mile per 234 watts.. which means that the 74,000 watt battery should do 74,000/234 = 316 miles. Now... the same concept applies. towing, driving at high speed etc will cause that 234 watts per mile to climb to say.. 300. in which case, your battery will only do 74,000/300 = 247 miles.
Hope that explains it.
Now... For EVs the concept is the same. The model Y has a 74 killowatt battery. that is 74,000 watts.. So Tesla expects their cars to do 1 mile per 234 watts.. which means that the 74,000 watt battery should do 74,000/234 = 316 miles. Now... the same concept applies. towing, driving at high speed etc will cause that 234 watts per mile to climb to say.. 300. in which case, your battery will only do 74,000/300 = 247 miles.
Hope that explains it.
That does help. I understand the variables that could have a major impact on efficiency: towing, weather, elevation, etc. I think for me it was that 234 wh number that baffled me. I c would see people post 250+ wh or something and not know what that meant, but in your example, that would go in and basically say instead of 316 miles, I'd then be averaging about 296 miles. I'm assuming the Tesla gives you this number as an average since last charge or something? I've driven one a few times, but this is one thing I haven't played around with much as far as the screen goes.
Also, I do plan to go alot off of the battery %, but at least for the first handful of months, I'll want to better understand what kind of efficiency my specific MY has since it feels like so many people are getting different numbers based on configuration obviously and their environments.
It takes some getting used to the terminology for sure. Coming from a gas car, you're used to efficiency being measured in miles per gallon. Not only are the units much different with electric, but you flip the numerator and denominator. A higher mpg number is better, but a lower Wh/mi number is better.
Instead of measuring how far you can go with a particular unit of energy, (miles traveled per gallon burned) in a Tesla you're seeing how many units of energy are consumed to go a particular distance (Wh consumed per mile traveled).
It's also a mental change due to the higher number on average. If you're used to, say, a 25 mpg car, then a bad efficiency tank may be 20 mpg. In a Tesla average may be 250 Wh/mi but that same bad trip jumps to 312 Wh/mi, which intuitively feels like a bigger drop even though statistically it's the same 80% of nominal.
Hope that helps.
Instead of measuring how far you can go with a particular unit of energy, (miles traveled per gallon burned) in a Tesla you're seeing how many units of energy are consumed to go a particular distance (Wh consumed per mile traveled).
It's also a mental change due to the higher number on average. If you're used to, say, a 25 mpg car, then a bad efficiency tank may be 20 mpg. In a Tesla average may be 250 Wh/mi but that same bad trip jumps to 312 Wh/mi, which intuitively feels like a bigger drop even though statistically it's the same 80% of nominal.
Hope that helps.
quadroplexor
Member
The other thing to consider with range when coming from gas powered cars, you don't fill it up to 100% unless you absolutely need to. This keeps from degrading the battery. There's some debate over "how full" you should limit the charging to. I keep mine at 80%. Obviously this impacts range. If most of your driving is around town and commuting, topping off nightly to 80% is plenty.
Flybuddy
Member
I had a Gen 2 Volt until recently which had no issue with full charging. The most influential factor on range was speed. The range would nearly double going 40 mph as opposed to 75 mph. Tesla seems to do better at highway speeds but still is more efficient at slower speeds.
Puma2020
Member
Like any ICE car, there are plenty of variables that control efficiencies. Most also apply to EVs. Jack rabbit starts (although a LOT more fun in an EV) does consume more energy. Seasons - Winter cold air is more dense than summer warm air. This also affects airplanes (lift). Speed is a major factor. I will include a chart that shows the range of a model 3 at a given speed. The Y being a bigger car than the 3, the values will be different but the chart does do a good job at showing the speed vs. range value. The faster you go the more air you have to push through, the lower range you will have. You can go 417 miles on a "full tank" if you drive 55 mph, but only 273 miles driving at 80 mph. Your choice. The wh metric that is thrown around is much like the mpg metric. However, the lower wh/mile value is better. At 200 wh/mi, you can go 5 miles on 1 kWh. At 300 wh/mi, you can only go 3.3 miles per kWh. Since you pay the electric utility for each kWh, that is a useful metric to use.
I also have a Gen 2 Volt in my household that is always charged to 100%. I have read the actual battery size is approx. 18kWh of which about 14kWh is usable. I would prefer the extra range option but GM built in the buffer, presumably to reduce battery degradation. Our 2016 has about 55K miles & I noticed no range loss however.
howardnj
Member
FWIW, on my 5th round trip from NJ to Florida I drove from Florence, SC to Pooler, Ga. A distance of 175 miles. I charged to 90% in Florence, SC and the following morning upon leaving, I had 87 or 86 % charge as Sentry was activated. Upon arriving in Pooler, Ga. I had a 5% charge left. This was the first time in over 14k miles on my Y that I ran down to a 5% charge and had a 27 mile range left. I was nervous and have no idea what my efficiency was? I have a list of over 50 charge stations along I95 between NJ and Florida and due to my age I need to stop every 150 miles or so to eat/snack, pee, and charge. I found Plug-Share to be very useful for long distance driving and always enter my next charge location so the vehicle warms the battery prior to my arrival.
After two years of ownership I still don't feel comfortable taking my MY on long trips. When I check route planners I come away thinking that's way too much trouble. I don't want to go below 20% ( 1/4 tank in my gas car) and since you don't charge over 80% on the road unless you want to be there a long time that means only using 60% of the battery/range. Way too many stops for me. Yes I'm old and need to go a lot but timing does'n always match. Also trips away from interstates are a but more tricky as chargers are not very prevalent. Perhaps in 10 yrs there will be many more chargers and traveling will be easier. Love the car around town.
Remember, even when you hit 0%, you can still drive quite a bit - report ranges around 20-30 miles depending on sources. NOT advocating to drive down to 0%, but it may help your range anxiety a bit if you face that situation.
I'm used to how Tesla reports battery level, and how it estimates range. I come back home with less than 10% pretty much every weekend after a long trip. The lowest I've been was 3% (2.7% to be exact), and I was ok since I knew the car would continue to drive past 0% if I end up there, and I was only few miles away from my home.
I'm used to how Tesla reports battery level, and how it estimates range. I come back home with less than 10% pretty much every weekend after a long trip. The lowest I've been was 3% (2.7% to be exact), and I was ok since I knew the car would continue to drive past 0% if I end up there, and I was only few miles away from my home.
In some cases Tesla Model Y owners have been able to drive about 10 or so miles beyond the displayed battery status of zero percent/zero miles. In other cases the Tesla Model Y has shut down without additional warning as the battery state of charge approached 0.
You may have been able to drive with less than 3% state of charge remaining but don't risk getting stranded. You might get within the length of a parking lot of a charging station before the Tesla Model Y shuts down, it might as well be miles away from the charging station. You can't easily push a 2000 kilo (4500 pound) vehicle to the charging station.
Do you have any video links of a case where as soon as you hit zero %, the car stopped? Not questioning you, just want to know if anyone has actually experienced.
I did look at about 10 different Youtube videos of running down until stopping, and all of them so far, gave some mileage after 0%.
Again, I'm not advocating to drive down to 0%, just saying that if you absolutely had no choice but to run it down to zero, you just might have some more mileage left.
No videos, they were probably too busy calling for roadside assistance.
You might have a few miles remaining but Tesla Model Y owners should not assume they can drive down to 0% state of charge and then another 10 or more miles. The ability to extract an extra few miles will vary with the temperature of the battery. That is a good reason not to try and find the limit.
Ciaopec
Active Member
Whoa! At this stage of the game you should feel comfortable with your EV. There is nothing that says you cannot charge above 80% nor anything that says stay above 20% I have over 160,000 EV miles OH-FL-IN-IL-NY: you name it I've been there. While driving those trips I rarely have need to charge above 55%; takes too much time. There was a time in 2016 and 17 when chargers were not as plentiful and once had to charger to nearly 100% but I planned that around a food stop. I will shoot for 10% arrival but comfortable enough (with plan B) to go to 5-7% on occasion. I don't think you should apply those "around town" kind of charge limits to cross county driving; it won't be a satisfying experience if you do. In August I'm hauling a bunch of furniture to INDY for my daughter in my MS. Then we're doing a round trip INDY-FL-INDY to pick up her Greyhound currently staying with us. We always have a great time. You should really try the experience . ANY Tesla is much more than an "around town" kind of car.
It appears you are the limiting factor here not your car.
How to plan a road trip - how long will it take?Here is a thread I read before I took my first 2016 road trip. Oldie but goodie: there are hundreds more if you search. ABRP is a great resource but make sure you plug in the pertinent data. Good luck and enjoy .
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