It's no secret that I have been pretty critical of several things Tesla has done recently. So it's only fair that I start a thread to highlight something pretty positive I think I've discovered as well.
I am fairly certain that Tesla is still tweaking and improving the P85D's efficiency (and perhaps other D's efficiency as well), either with improvements to the torque sleep algorithms or through other means. I will provide data to support this, along with a fairly thorough explanation of the data.
For quite some time, I have been recording every trip my wife makes in the Model S to and from work, as well as every trip I make in the Model S along a very similar route. I record range miles used, total energy used, and average energy used, as well as estimated temperature and estimated wind speed, other weather conditions, etc.
Her trip to work, northbound, is approximately 53.5 miles long, and her trip home, southbound is approximately 53 miles long. There is a drop in elevation of 754 feet northbound, and an increase in elevation of 754 feet southbound. The elevation changes do not take into account our long, fairly steep driveway and the parking garage she parks in at work.
My trip northbound is approximately 58.4 miles long, and my trip southbound is approximately 58 miles long. There is a drop in elevation of 630 feet northbound, and an increase in elevation of 630 feet southbound.
The two trips are identical for 90-95% of the distance traveled. Roughly half the time is spent on an interstate highway, with a speed limit of 65 MPH, and the other half of the trip is spent on rural roads with speed limits varying from 25 MPH to 50 MPH, with some traffic lights through towns, etc. Her trip usually takes her between 60 and 65 minutes. My trip usually takes me between 66 and 71 minutes.
My wife sets her TACC speed to 68 and I set mine to 70 on the highway. Neither of us use it off the highway. I probably drive somewhat more aggressively than she does, but not significantly so. I do weigh quite a bit more than she does, and am also usually travelling with our labrador retriever and her crate, my tennis bag, etc. I actually attempt to record the weight in the cabin, and the difference is generally 250 pounds or so. I set the temperature to max cooling (62 degrees) and she sets the temperature to 66 degrees.
Below are each of our average Wh/mi for our northbound and southbound legs on versions 6.2.2.4.236 and version 6.2.2.4.250 of the firmware. I believe there are enough total legs recorded and the weather conditions were similar enough that the efficiency improvement shown is significant, and due to a change made in the firmware. Our tires were just over a month old at the point we received .236, meaning they would have had over 1500 miles on them, so I don't think the improvement in efficiency could be attributed to decreased rolling resistance from tread wear. In fact, I did make a change that should work in the direction opposite the efficiency improvement, in that part way into .236 I decreased the tire pressure from 50 psi to 45 psi, based on Tesla having again changed the recommended tire pressure for the P85D. (I was a little late in making the adjustment back.) If anything, this would bias the efficiency a bit towards being better in .236.
I'm happy to try to answer any questions.
I know there will be people who say this isn't enough data to form any conclusions, and that the improved efficiency could be due to weather, different driving styles, etc. To that I say you could certainly be correct. I'm trying to supply the data as objectively as possible, so I have broken the data down by driver and leg. I don't imagine our individual driving styles have changed over the time period in question. I think there are enough legs to account for the slight changes in weather (temperature, wind, etc.) so that any weather impact would come out in the wash, so to speak.
Here's the data:
I am fairly certain that Tesla is still tweaking and improving the P85D's efficiency (and perhaps other D's efficiency as well), either with improvements to the torque sleep algorithms or through other means. I will provide data to support this, along with a fairly thorough explanation of the data.
For quite some time, I have been recording every trip my wife makes in the Model S to and from work, as well as every trip I make in the Model S along a very similar route. I record range miles used, total energy used, and average energy used, as well as estimated temperature and estimated wind speed, other weather conditions, etc.
Her trip to work, northbound, is approximately 53.5 miles long, and her trip home, southbound is approximately 53 miles long. There is a drop in elevation of 754 feet northbound, and an increase in elevation of 754 feet southbound. The elevation changes do not take into account our long, fairly steep driveway and the parking garage she parks in at work.
My trip northbound is approximately 58.4 miles long, and my trip southbound is approximately 58 miles long. There is a drop in elevation of 630 feet northbound, and an increase in elevation of 630 feet southbound.
The two trips are identical for 90-95% of the distance traveled. Roughly half the time is spent on an interstate highway, with a speed limit of 65 MPH, and the other half of the trip is spent on rural roads with speed limits varying from 25 MPH to 50 MPH, with some traffic lights through towns, etc. Her trip usually takes her between 60 and 65 minutes. My trip usually takes me between 66 and 71 minutes.
My wife sets her TACC speed to 68 and I set mine to 70 on the highway. Neither of us use it off the highway. I probably drive somewhat more aggressively than she does, but not significantly so. I do weigh quite a bit more than she does, and am also usually travelling with our labrador retriever and her crate, my tennis bag, etc. I actually attempt to record the weight in the cabin, and the difference is generally 250 pounds or so. I set the temperature to max cooling (62 degrees) and she sets the temperature to 66 degrees.
Below are each of our average Wh/mi for our northbound and southbound legs on versions 6.2.2.4.236 and version 6.2.2.4.250 of the firmware. I believe there are enough total legs recorded and the weather conditions were similar enough that the efficiency improvement shown is significant, and due to a change made in the firmware. Our tires were just over a month old at the point we received .236, meaning they would have had over 1500 miles on them, so I don't think the improvement in efficiency could be attributed to decreased rolling resistance from tread wear. In fact, I did make a change that should work in the direction opposite the efficiency improvement, in that part way into .236 I decreased the tire pressure from 50 psi to 45 psi, based on Tesla having again changed the recommended tire pressure for the P85D. (I was a little late in making the adjustment back.) If anything, this would bias the efficiency a bit towards being better in .236.
I'm happy to try to answer any questions.
I know there will be people who say this isn't enough data to form any conclusions, and that the improved efficiency could be due to weather, different driving styles, etc. To that I say you could certainly be correct. I'm trying to supply the data as objectively as possible, so I have broken the data down by driver and leg. I don't imagine our individual driving styles have changed over the time period in question. I think there are enough legs to account for the slight changes in weather (temperature, wind, etc.) so that any weather impact would come out in the wash, so to speak.
Here's the data:
.236 (June and July) | Legs | .250 (July and August) | Legs | |
Kim- North | 260 | 11 | 243 | 6 |
Kim- South | 300 | 11 | 295 | 6 |
Andy- North | 270 | 5 | 263 | 2 |
Andy- South | 326 | 5 | 315 | 2 |
Kim- All | 280 | 22 | 269 | 12 |
Andy- All | 298 | 10 | 289 | 4 |
Overall | 286 | 32 | 274 | 16 |