Same 324 mile drive - huge difference in efficiency

[Zoomit]

I see your point. How did you get to 36%?

Here is my lifetime stats of Wh/Mile and I can't vouch for how much of this has been with headwind or tailwind but the difference is about 10% on average for a +/- 10 mph difference.

The 36% number came from a Model 3 driving consumption tool I created to do my own route planning calculations. It's pretty close but certainly not exact.

Unfortunately, I wouldn't infer wind effects from that TeslaFi Wh/mi data. Here's my chart from over 60,000 miles with my Model 3. I can assure you that driving at a steady 70 mph is not more efficient than driving at 55 mph as one could interpret from this data.

 

[Y_4_speed]

Thanks

So I was hoping my data would show this but there is something still missing I think.

I have 10% difference in efficiency because the temperature (high 90-ies vs low 70-ies), 78.8% versus 68.8% efficiency. Then assuming I had full 10 mph head wind this week and 10 mph tail wind in May that put my relative speed at 68 mph versus 52 mph for an efficiency of 312 versus 279 Wh/mi or 12%. Adding those two up give me 22% but no the actual 34% I lost. Maybe I'm giving too much credit to the TeslaFi data.

 

[FloridaSun]

Since I got my car in March 2020 I've traveled a few times between my home in Frisco, TX and Fayetteville, AR and know pretty well when and where to stop to make it a pleasant drive. Going through Oklahoma takes some careful planning but there are few good Chademo chargers along the way and A Better Route Planner is helpful.

On my recent trip back from Fayetteville yesterday I got in major trouble and I had to make an emergency stop to charge and still only made it back home with 2 percent left. The super low efficiency caught me off guard. The energy graph has impressed me many times on how accurate it is at predicting usage but this time it was off the charts. Every few minutes it kept dropping another percent.

Here are some stats from TeslaFi:
Distance 324 miles
Altitude loss 739 ft
110.89 KWH used for an Wh/mile of 361
Average speed 58 mph
Outside temperature between 86-98 F and no precipitation
light wind between 10-13
SW 2021.12.25.7

In comparison the opposite direction driven the day before with at least 200 lbs of additional weight (moving my girl to college) used 93.49 KWH (296 Wh/mile) with an outside temp of 88 F, That is a difference in efficiency of 22%.

Another point of reference is my last trip back from Fayetteville in May:
Same distance and altitude loss
88.99 KWH used for an Wh/mile of 269
Average speed 62 mph
Outside temperature between 71-76 F and no precipitation
light wind between 10-15
SW 2021.4.15

The difference in efficiency is 34% for the exact same trip and that does not make sense to me.

My lifetime average is 293 Wh/mi over 14,470 miles.

Any idea what is going on?!?!

Not surprised.. The AC pulls a lot of power when it's hot.. Your difference in consumption was likely due to AC consumption and potentially battery cooling.
I drive, whenever it's not unbearable with the AC off so that I have to charge less frequently.. I can only do this if I'm alone in the car.. With my family in the car, they would be complaining that it's too hot. Especially for short trips around town, the difference is like night and day.. For a short 5 mile trip in 93 degrees with sunshine and the AC set to 71 degrees, I'll get 350 wh/mile at best.. If I do the same trip without AC, I can get sub 200 Wh/mile..m
Roof sunshade with blackout will help a little bit with AC consumption..
The main problem is that the glass roof will heat up the car if it's sunny and the AC has to pull a lot of power to keep it cool. On a cloudy day with the same temperature, you will see significantly lower consumption.

 

[Big Earl]

Head wind vs. tail wind. I always check the wind forecast before setting out for the day. www.windy.com

 

[FloridaSun]

Not surprised.. The AC pulls a lot of power when it's hot.. Your difference in consumption was likely due to AC consumption and potentially battery cooling.
I drive, whenever it's not unbearable with the AC off so that I have to charge less frequently.. I can only do this if I'm alone in the car.. With my family in the car, they would be complaining that it's too hot. Especially for short trips around town, the difference is like night and day.. For a short 5 mile trip in 93 degrees with sunshine and the AC set to 71 degrees, I'll get 350 wh/mile at best.. If I do the same trip without AC, I can get sub 200 Wh/mile..m
Roof sunshade with blackout will help a little bit with AC consumption..
The main problem is that the glass roof will heat up the car if it's sunny and the AC has to pull a lot of power to keep it cool. On a cloudy day with the same temperature, you will see significantly lower consumption.

Today, it was cloudy and mid 80's and I drove without the AC around town and this is the efficiency that I got..

 

[Pianewman]

^^^must've been driving SOUTH the whole time!

 

[sleepydoc]

If you’re cruising on the highway a heavier car can actually help you since you have more inertia.

I agree with the others - A/C can make a significant difference, as can headwinds. Once your speeds increase above 50-55 mph your wind resistance & drag increase significantly.

 

[FloridaSun]

If you’re cruising on the highway a heavier car can actually help you since you have more inertia.

I agree with the others - A/C can make a significant difference, as can headwinds. Once your speeds increase above 50-55 mph your wind resistance & drag increase significantly.

On my 3109 mile road trip, skies were mostly cloudy on my first travel day and despite driving 80 mph wherever possible, consumption did not exceed 300 wh/mile.
However, on my last trip leg from Kingsville to McAllen/TX, temperature was 96F and consumption went from 295 Wh/mile for the previous 1200 miles to 335 Wh/mile.. Flat terrain.. Only difference was sunshine and heat

 

[GtiMart]

Since you're doing the same trip in the same direction, elevation is the same so that doesn't count. Otherwise elevation is an important factor. Temperature is clearly a factor as you've all been discussing. I just want to say that wind is in my opinion the biggest factor. It's the direction of the wind that you must look at. See this nice article by ABRP: Wind Influence on Tesla Model 3 Even side winds are detrimental, although to a lesser extent.

 

[Y_4_speed]

Since you're doing the same trip in the same direction, elevation is the same so that doesn't count. Otherwise elevation is an important factor. Temperature is clearly a factor as you've all been discussing. I just want to say that wind is in my opinion the biggest factor. It's the direction of the wind that you must look at. See this nice article by ABRP: Wind Influence on Tesla Model 3 Even side winds are detrimental, although to a lesser extent.

That is a great article. Thanks for sharing.

Now if only Tesla could step up their game. They have all the facts they need to improve the estimated range graph and consider inside/outside temperature and wind in their prediction model.

 

[Exelion]

Incredible. A variation from +6% to -19% is a lot more than I thought. And! Not to mention the graph is based on the model 3, the model Y would be more affected by winds, so the numbers would be greater I'm sure.

The part about sidewinds surprised me the most - 8% loss!

 

[BrownOuttaSpec]

@Y_4_speed
I feel like we have it "figured out" with the heat and the wind.... but is something rubbing/scraping on your suspension? this doesn't look right (maybe just a weird shadow?):

 

[GtiMart]

@Exelion , and that report uses data at speeds of 100-120kph (62-75mph), higher speeds will be worse. Aerodynamics are complex. I think there's something about a thin layer of air that stays close to the car and helps aero. With sidewinds, I think this thin layer gets disturbed and that's what augments drag. I'm not an expert, if you're interested you can look for Kyle.engineers on youtube, he's an expert and has some videos that explain it.

The same physics hold true for ICE cars, but the factor in overall consumption is less important because the other parts are less efficient (mainly the engine).

 

[Y_4_speed]

@Y_4_speed
I feel like we have it "figured out" with the heat and the wind.... but is something rubbing/scraping on your suspension? this doesn't look right (maybe just a weird shadow?):
View attachment 697954

Wow. Good eye sight! I think it is a bit of plastic from when I painted the calibers. It is long gone by now.

 

[Pianewman]

Recent road trip, west of Fort Worth. Cross winds killed consumption. Same thing would happen with my 48-52mpg "clean" (HAHAHA) diesel Passat. Similar tracking issues, as well, as crosswinds make driving in a straight line more difficult. With the Tesla, numbers went from 290wh/mi to 330wh/mi, crosswind only 10-12mph.

 

[GtiMart]

That's what makes planning a trip in an EV a bit more difficult. If you plan a lot in advance, you cannot know the temperature and wind speed+direction. In those cases I input (in ABRP) something on the negative end of the spectrum, not worse case scenario but something in that sense. I re-plan just a bit before departure to validate the plan. In any case, I monitor what's happening live and drive one leg at a time.
If you plan for the next day you have access to the information using weather apps or things like the Windy app which is great.

 

[Pianewman]

ABRP: reference consumption, I input 320-330, but lifetime average is 283wh/mi, at 13k miles.

Interesting going from Denver to Alamosa, through Aspen,(gained about 2.5k feet) tooling around Aspen , up and over Independence Pass (12k feet). All downhill to Alamosa, ended up with 267wh/mi for that leg (Denver-Alamosa) of my trip. I thought the drive UP to Aspen, UP Independence Pass would kill the wh/mi average, but the recovery going downhill was remarkable.

 

[GtiMart]

Yeah, elevation makes a difference for sure, but if you go back down you gain a good amount of what was lost. I think regen is in the area of 80% efficient.

 

[Pianewman]

Long time Tesla drive (Model 3) thought it was more like 60%. Hard to quantify. I guess we can say 60-80% recovery, unless...unless you're encountering strong UPDRAFTS going down the mountain. (Jeez...really picking the fly s**t out of the pepper now!!!)

 

[Ken_Y]

Probably temperature. It isn't just the AC but the heat pump and cooling mechanism for the battery has to work much harder. I went to Zion via LV and it hit 120F on both legs. My efficient dropped to 350wh/mi causing me to have to top up twice. Otherwise, I would have been able to make it with a single charge between Zion to LV and LV to Vermo.