Poll: Model 3 Efficiency (Battery-to-Wheels)

[KenF]

Sorry, nope

Thermodynamics 101? Something that looks black is highly emissive for certain wavelengths, but not necessarily for wavelengths where thermal emission happens.

Insulation is obviously a factor as well. In summer, in the sun, a black t-shirt will feel much warmer than a white t-shirt. But, in winter, in the sun, does a white insulated jacket feel noticeably warmer than a black insulated jacket? Probably not.

 

[KenF]

I would think interior color would matter way more than exterior color, especially with all the glass on Model 3. My midnight silver would hardly be considered a light color.

No question, in the summer, a white or metallic silver M3 with a white interior is the best for efficiency. Though I am still unclear about the requirements of the HVAC system — is it closer to 10wh/m or 30wh/m to maintain 70 degrees in 90-degree weather?

 

[nvx1977]

No question, in the summer, a white or metallic silver M3 with a white interior is the best for efficiency. Though I am still unclear about the requirements of the HVAC system — is it closer to 10wh/m or 30wh/m to maintain 70 degrees in 90-degree weather?

keep in mind that efficiency is an energy measure based on mileage, whereas HVAC draw is an energy measure based on time. Which means the impact it has on the efficiency number depends on how fast you are traveling. The slower you go, the more the HVAC will have an impact on your efficiency. Another way to think about this is: the faster you get to your destination, the less time the HVAC has to use energy.

I also don't believe that the temperature delta between ambient and set point affects significantly energy usage of the compressor. With HVAC in auto mode and assuming cooling set point, the A/C compressor is constantly running, and only the fan speed controls the rate of cooling. I'm not 100% sure if the compressor has variable energy capabilities, meaning it uses less energy if delta T is low. But my own observations is that even when delta T is low or even slightly negative, the compressor still runs, and it's a significant draw. What's even more annoying is that if delta T becomes slightly more negative, the heaters kick in, with no visual warning if you don't have climate control settings visible.

Consider this scenario, common here in New England summers:

During the day, ambient temps are around 80-90F. In the evening, it sharply drops into the high 60s. If your set point is 72F, and you set HVAC to auto, at some point in the evening when ambient is 69F, suddenly your car is in heating mode and it engages the heaters. So if you take the car out in the evening, you have to either shut off HVAC, or reduce your set point to prevent the heaters from coming on.

This is my biggest gripe about HVAC in auto. I'm unnecessarily losing efficiency when ambient and set point are close. All of spring and fall, and summer evenings are very comfortable. I'm leaving HVAC off during these times.

 

[SageBrush]

keep in mind that efficiency is an energy measure based on mileage, whereas HVAC draw is an energy measure based on time. Which means the impact it has on the efficiency number depends on how fast you are traveling. The slower you go, the more the HVAC will have an impact on your efficiency. Another way to think about this is: the faster you get to your destination, the less time the HVAC has to use energy.

Yep,
This is one of the reasons I drive a little faster in the summer.
The other is that air density decreases in my summer due to higher temperature and humidity, leading to a lower overall contribution of Wh/mile from Aero than in other seasons and a higher relative contribution from road friction and A/C. These latter two are either not affected by, or improved with faster speeds. I'm not saying that a faster speed leads to lower Wh/mile, but that the efficiency hit from a higher speed is less in the summer.

 

[KenF]

Consider this scenario, common here in New England summers:

During the day, ambient temps are around 80-90F. In the evening, it sharply drops into the high 60s. If your set point is 72F, and you set HVAC to auto, at some point in the evening when ambient is 69F, suddenly your car is in heating mode and it engages the heaters. So if you take the car out in the evening, you have to either shut off HVAC, or reduce your set point to prevent the heaters from coming on.

This is my biggest gripe about HVAC in auto. I'm unnecessarily losing efficiency when ambient and set point are close. All of spring and fall, and summer evenings are very comfortable. I'm leaving HVAC off during these times.

Thanks for the informative post. So, what it sounds like we really need in the M3 is a Nest-like thermostat control to turn off the compressor if the indoor ambient temperature is within a range we set (e.g., +/- 3 degrees of our desired temperature).

 

[djole]

Yikes. 30% overhead.

But, just to clarify... what types of on-board energy consumption are actually excluded from the trip meter?

From what I've read, I'd agree vampire losses are not counted. And I think I also saw in a thread somewhere that pre-conditioning HVAC loads while the car is "off" aren't counted either.

But surely battery conditioning and HVAC loads while the car is on -- moving or not -- are counted towards the kWh consumption figures on the trip meter, right???

Mine is 32% overhead. The question about counting in HVAC load while the car is on is very important. I would like to know the answer!

 

[jsmay311]

Mine is 32% overhead. The question about counting in HVAC load while the car is on is very important. I would like to know the answer!

Yikes! I hope these kinds of numbers aren't typical!

I had been hoping that the super high Wh/mi numbers reported by Edmund's Long Term testing (368 Wh/mi last month(!) and a lifetime average of 318 Wh/mi) was just some kind of fluke or severe outlier. But if your numbers are typical, then the Edmund's numbers are probably legit (and depressing).

 

[nvx1977]

Yikes. 30% overhead.

But, just to clarify... what types of on-board energy consumption are actually excluded from the trip meter?

From what I've read, I'd agree vampire losses are not counted. And I think I also saw in a thread somewhere that pre-conditioning HVAC loads while the car is "off" aren't counted either.

But surely battery conditioning and HVAC loads while the car is on -- moving or not -- are counted towards the kWh consumption figures on the trip meter, right???

Car will count battery conditioning and HVAC in the efficiency reading if you are sitting in the car. But it's nuanced. the following are my observations:

If you are outside of your car, and you start climate control, the instant you open the door, the HVAC switches to the last in-car use settings. At the point of that switchover, the HVAC energy use is starting to count against your imminent drive, unless you decide to not get in the car and shut the door. Let's say you get in, and you decide to check your phone for 5 minutes without driving. The HVAC is running and is using energy. Then, you press on the brake. This resets the last trip efficiency numbers to zero. However the car is still tracking HVAC energy usage since you got in. Shortly after you start moving, you'll notice horrendous efficiency reading. This is due to huge numerator (Wh) and small denominator (mi). The Wh number is way high because of that 5 minutes of HVAC use while parked.

Notably, the preconditioning while you were outside of the car is not factored in at all. Same for vampire drain or other energy consumption that occurs when you are outside of the car. Naturally these events still affect your state-of-charge reading on the battery.

So the efficiency readings on the car is really to give you an idea of how you're doing when you're traveling.

 

[Zythryn]

Yikes! I hope these kinds of numbers aren't typical!

I had been hoping that the super high Wh/mi numbers reported by Edmund's Long Term testing (368 Wh/mi last month(!) and a lifetime average of 318 Wh/mi) was just some kind of fluke or severe outlier. But if your numbers are typical, then the Edmund's numbers are probably legit (and depressing).

Please note, the Edmunds numbers are measured from the wall, not the onscreen display. Depending upon how they are charging, this can be a 8% to12% loss.
Not sure about LA, but parts of CA have had a very hot summer so far. I would not be surprised if their AC has been running a lot.
I haven't seen anything like that, but then again, I am not in LA

 

[jsmay311]

Please note, the Edmunds numbers are measured from the wall, not the onscreen display. Depending upon how they are charging, this can be a 8% to12% loss.
Not sure about LA, but parts of CA have had a very hot summer so far. I would not be surprised if their AC has been running a lot.
I haven't seen anything like that, but then again, I am not in LA

Yeah, that's what we were talking about.

Edmunds only reported the onboard consumption (screen) Wh/mi number for their first monthly report back in January '18. That month the "screen" number was 251.7 Wh/mi and the "wall" number was 302 Wh/mi, which is 20% higher than the screen number. Some of that is certainly due to charging losses and some is certainly vampire losses. Not sure what else might've contributed tho.

 

[SageBrush]

Some of that is certainly due to charging losses and some is certainly vampire losses. Not sure what else might've contributed tho.

Charging sessions that involve only small amounts of energy transfer are inefficient.

 

[jsmay311]

Car will count battery conditioning and HVAC in the efficiency reading if you are sitting in the car. But it's nuanced. the following are my observations:

If you are outside of your car, and you start climate control, the instant you open the door, the HVAC switches to the last in-car use settings. At the point of that switchover, the HVAC energy use is starting to count against your imminent drive, unless you decide to not get in the car and shut the door. Let's say you get in, and you decide to check your phone for 5 minutes without driving. The HVAC is running and is using energy. Then, you press on the brake. This resets the last trip efficiency numbers to zero. However the car is still tracking HVAC energy usage since you got in. Shortly after you start moving, you'll notice horrendous efficiency reading. This is due to huge numerator (Wh) and small denominator (mi). The Wh number is way high because of that 5 minutes of HVAC use while parked.

Notably, the preconditioning while you were outside of the car is not factored in at all. Same for vampire drain or other energy consumption that occurs when you are outside of the car. Naturally these events still affect your state-of-charge reading on the battery.

So the efficiency readings on the car is really to give you an idea of how you're doing when you're traveling.

Hm... I can't remember the places where I'd read about the on-board kWh meter not counting power draws when stationary.

But I do remember one source that claimed that battery conditioning while driving is NOT counted: the guys that did the 606 mile hypermile test. They only got 66 kWh out of their battery before it died per the on-screen trip energy meter display, and when they asked their local Tesla folks (I'm assuming at their local SC) why they didn't get more energy out of the pack, they were told that energy consumed by the BMS/TMS is not counted on the on-screen number.

They talk about it here @8:10:

That said, this forum is rife with examples where Tesla reps gave out false information. So I wouldn't say that story is conclusive by any means.

 

[jsmay311]

Charging sessions that involve only small amounts of energy transfer are inefficient.

True, but if we're focusing on the Edmunds numbers, they aren't doing small or frequent charges.

In January they drove 1388 miles and only charged 14 times, which works out to 99 miles per charging session.

Through May, they had driven 6009 miles and had 57 charging sessions for an average of 105 miles per charging session. (They didn't say how many times they charged in June.) That's gonna be a lot more miles between charges than the average person who plugs in every night.

 

[nvx1977]

I can't prove it, but I drive the same route everyday in very similar conditions. When temps got into the high 90s here in New England (which doesn't happen often), I sucked it up and kept HVAC off to see if my efficiency would remain about the same. It didn't. Very notable increase in the Wh/mi number (from 170s to low 200s). There's no other explanation for this except for the battery conditioning. If temps are in the 80s, efficiency is always in the 170s and lower.

Another time this happened (super hot, low 200Wh/mi), I got hit by a thunderstorm that significantly cooled ambient temps, and after that, my efficiency started to recover and eventually settled back into the 170s by the end of the drive.

So I feel this is pretty compelling evidence that the battery conditioning does show up. Now, if you were running cabin A/C during that time, I suspect the impact of the battery conditioning would be really hard to see. I didn't watch the vid; did they mention if they ran HVAC? I would imagine for that kind of hypermiling, they'd be smart enough to shut it off.

 

[djole]

I am really frustrated by the "wall to wheels" efficiency, which is in my case about 32% average for more than 1000 miles. I switched to km to have better resolution. This is what i had yesterday:

My battery drop was 67km, i drove 58.3km, the efficiency battery to wheels was 140Wh/km, and wall to wheels was 186Wh/km (32.8% increase). Colleague of mine has also model 3, and he was driving same distance, and he was charging on same charger. His efficiency was lower, he probably had AC on, and more hills or whatever, and his efficiency was 160Wh/km. but he also had 58km and battery drop of 67km and he also used 10.8kWh to charge, but his wall to wheels increase was only 16.2%. It looks like the vampire drain on my car had huge effect on "wall to wheels" efficiency.

 

[jsmay311]

Car will count battery conditioning and HVAC in the efficiency reading if you are sitting in the car. But it's nuanced. the following are my observations:

If you are outside of your car, and you start climate control, the instant you open the door, the HVAC switches to the last in-car use settings. At the point of that switchover, the HVAC energy use is starting to count against your imminent drive, unless you decide to not get in the car and shut the door. Let's say you get in, and you decide to check your phone for 5 minutes without driving. The HVAC is running and is using energy. Then, you press on the brake. This resets the last trip efficiency numbers to zero. However the car is still tracking HVAC energy usage since you got in. Shortly after you start moving, you'll notice horrendous efficiency reading. This is due to huge numerator (Wh) and small denominator (mi). The Wh number is way high because of that 5 minutes of HVAC use while parked.

Notably, the preconditioning while you were outside of the car is not factored in at all. Same for vampire drain or other energy consumption that occurs when you are outside of the car. Naturally these events still affect your state-of-charge reading on the battery.

So the efficiency readings on the car is really to give you an idea of how you're doing when you're traveling.

FYI... I just did a test (I finally have a M3 now(!)), and found that when the car is stopped but still in Drive, HVAC power DOES count towards the displayed trip energy consumption and Wh/mi figures. But if you're in Park, even if you're still sitting in the drivers seat, the HVAC loads are NOT counted in the trip energy consumption.

(This test was done in the middle of a drive, not at the beginning of a drive, so I suppose there could be some different behavior at the start of a drive.)

 

[nvx1977]

FYI... I just did a test (I finally have a M3 now(!)), and found that when the car is stopped but still in Drive, HVAC power DOES count towards the displayed trip energy consumption and Wh/mi figures. But if you're in Park, even if you're still sitting in the drivers seat, the HVAC loads are NOT counted in the trip energy consumption.

(This test was done in the middle of a drive, not at the beginning of a drive, so I suppose there could be some different behavior at the start of a drive.)

Yes, I believe middle of a drive PARK status keeps the HVAC usage in the calculations. Butt out of the seat (car off situation) will stop it, which also will reset the current drive trip meter (next time you drive). If you put the car in park without getting out, the current drive trip meter doesn't reset, and the HVAC calc continues.

Congrats on your Model 3!

 

[jsmay311]

Unfortunately, after only 26 hours of ownership I can personally attest that the most effective way to minimize your Wh/mi is to blow up your drive unit (I'm guessing that's what happened at least) and then have it loaded onto a flatbed and driven 30 miles to the service center.
0 Wh/mile!



I know this isn't the right place to post about this, but if anyone can point me to a thread where someone has reported trying to do a hard acceleration and then hearing a loud bang from the rear of the car followed by violent shuddering and the speedometer going all over the place with no power to the wheels, if you could point me at that thread I'd greatly appreciated it.

 

[Ed++]

Dual motor non-perfornamce, 18 inch areo wheels, tire pressure set cold at 44 lbs when I picked it up. I do not have Version 9 software yet.
Battery to wheels: 1289 mi, 271 kWh, 210 Wh/mi
Wall to wheels: 1289 mi, 311.2 kWh, 241 Wh/mi
I am very happy with these numbers. Love the car!

I have had my Model 3 11 days. I usually try to drive it fairly efficiently, adjust the accelerator petal so that it is "coasting" where I can, accelerate slowly, use the regenerative braking as much as possible. Almost always drive the speed limit, and sometimes slower. But I also floor it sometimes, especially when I am giving a demo. I also have used the air conditioning a fair amount since it was hot the first week I had it (Louisville, KY area). It is getting cold now, so I expect if I start using the heater much my Wh/mi will go down quite a bit.

 

[SageBrush]

It is getting cold now, so I expect if I start using the heater much my Wh/mi will go down quite a bit.

True for the cabin heater, so I use gloves and seat heating.