Actual rated wh/mi

[JerseyShoreMY]

No. The link above shows for the LR Non-Performance Model Y they drew 78.5kWh from the vehicle (including basically the entire buffer). That's all the pack has, period. There's nothing else. The Model Y Performance 2021 has a larger pack (closer to 81kWh available - the data is available on the above linked site).

The buffer is always located below 0%, and for Model 3 it is 4.5% of the nominal full pack (and I THINK it is 4.5% for Model Y as well - SMT would tell you and I'm sure someone has posted the data for a Model Y). So at 0% your car will be very upset, but the BMS will think that you have a bit over 3kWh left before you're done. And if you're extremely lucky you might be able to use some or all of that. I wouldn't try though (see above test for the variability).

There is no top end buffer, though if you look at one of my other posts today Tesla does apparently have a way of "squeezing" extra energy into a fixed number of rated miles when the car is brand new with a very energetic pack that exceeds their expectation of the design capacity. But even in that scenario, your rated miles will start clicking down immediately...they'll just click down more slowly (slower by 1-2%, so imperceptible) when the car is brand new. No top buffer.

We have charged our MY up to 84% on the 120V charger. When we removed the charge set about 25 minutes before the estimated end of cycle, it was just then showing 84% charge state. But after disconnecting the charger cable, the battery continued to rise all the way to 87%.
Anyone else ever see this % rise after removing the charging cable?
Is it likely a part of the buffer requirement for the design capacity?

 

[jcanoe]

We have charged our MY up to 84% on the 120V charger. When we removed the charge set about 25 minutes before the estimated end of cycle, it was just then showing 84% charge state. But after disconnecting the charger cable, the battery continued to rise all the way to 87%.
Anyone else ever see this % rise after removing the charging cable?
Is it likely a part of the buffer requirement for the design capacity?

This is normal. Periodically the Tesla vehicle's battery management system will perform cell re-balancing at the end of the charging session.

 

[Swoosh99]

Yes that is basically true. As mentioned above.

Note that for “reasons” the rated line is 5Wh/mi higher than the actual charging constant.

And because of the buffer you have to be 4.5% lower than that constant for mile-for-mile rolloff.

And because of heat losses you have to be about 1% lower than that as measured on the trip meter.

So for the non-P Model Y take 77.8kWh or so and divide by the rated miles on the Tesla website (whatever the true adjusted max rated range is for the vehicle). That will give you the charging constant.

When the vehicle is new and the energy exceeds the degradation threshold, you’ll be able to use a little more per mile and still achieve parity, since the rated mile energy content will be slightly inflated. (For example you might have 78.5kWh at 100% rather than 77.8kWh, in which case your rated miles will have 1% more energy than later in life, to hide initial capacity loss.)

So for Model Y with 77.8kWh battery with rated range of 326mi initially the constant is about 239Wh/mi. Line on energy screen is probably about 244Wh/mi.

And if you show some rated range loss, you need to get about 226Wh/mi on the trip meter for mile-for-rated-mile “parity.”

That's good info. I've been obsessing over my efficiency since I got the Model Y standard range. It should have been more miles than I needed because I do mostly city driving but for some reason my efficiency is so much worse than highway driving. I thought the opposite supposed to be true with EVs but when I'm driving on a typical day in an urban city with stop/go traffic, my wH/mi can average about 400wH/mi. At this rate, my standard range can only realistically go about 100mi in the city....such a bummer

 

[jcanoe]

That's good info. I've been obsessing over my efficiency since I got the Model Y standard range. It should have been more miles than I needed because I do mostly city driving but for some reason my efficiency is so much worse than highway driving. I thought the opposite supposed to be true with EVs but when I'm driving on a typical day in an urban city with stop/go traffic, my wH/mi can average about 400wH/mi. At this rate, my standard range can only realistically go about 100mi in the city....such a bummer

Hawaii has a hilly terrain. That would account for some of the additional energy usage.

Hawaii is tropical with lots of sun; the AC is working hard to cool the Model Y's battery pack and the passenger cabin. (You may want to have a high quality tint film installed on the windshield, front windows and rear hatch glass. Some Model Y owners also add tint to the glass roof although the roof has a factory tint that rejects UV and IR you can improve on the factory tint. There are also sun shades that can be installed on the inside for the roof and also the rear hatch glass (most useful if you have a 7 seat Model Y.)

Leadfoot; it is very tempting to go fast in a Tesla vehicle.

 

[dino007]

Lots of good info here, just to add i been averaging about 300wH/mi here in 100 degree weather in texas so far on a full charge to like 10% got 205 miles mixed city highway

From 85% to like 15% about 175 miles about the same 305wH/mi
Windows tinted all around and windshield
I educated myself pretty well of not expecting the 326 bs range so i ain't fretting and I don’t necessarily drive conservative all the time anyways so i underStand my range

didnt see an answer on this does the A/C fan speed matter in an electric vehicle unlike a gas powered which doesn’t cause the compressor is on regardless, is it the same way?

 

[PNWLeccy]

That's good info. I've been obsessing over my efficiency since I got the Model Y standard range. It should have been more miles than I needed because I do mostly city driving but for some reason my efficiency is so much worse than highway driving. I thought the opposite supposed to be true with EVs but when I'm driving on a typical day in an urban city with stop/go traffic, my wH/mi can average about 400wH/mi. At this rate, my standard range can only realistically go about 100mi in the city....such a bummer

This is interesting because I have a MY SR on order. My 2018 LR RWD seems to have much higher wh/mi than others with the same vehicle (Lifetime 282wh/mi) and I suspect it is because I do lots of short drives in the city. That seems to give me pretty high numbers but when I go on a longer 100mi.+ trip with lots of freeway driving, my numbers are closer to the 240-260wh/mi range.

I am wondering how the MY will compare since I had the less efficient 19" wheels on the M3 and it doesn't have a heat pump.

 

[AlanSubie4Life]

That's good info. I've been obsessing over my efficiency since I got the Model Y standard range. It should have been more miles than I needed because I do mostly city driving but for some reason my efficiency is so much worse than highway driving. I thought the opposite supposed to be true with EVs but when I'm driving on a typical day in an urban city with stop/go traffic, my wH/mi can average about 400wH/mi. At this rate, my standard range can only realistically go about 100mi in the city....such a bummer

You can relatively easily measure the mile-for-rated-mile value by paying careful attention to rated mile use and trip meter use on a single long trip segment. It is pretty straightforward math to verify the approximate target number.

lots of short drives in the city.

Yeah these trips just have high overhead from initial heating or cooling transients. Also combining that startup transient with slow speeds does not help. It is avg wattage/speed that you calculate to give you Wh/mi…

 

[jcanoe]

didnt see an answer on this does the A/C fan speed matter in an electric vehicle unlike a gas powered which doesn’t cause the compressor is on regardless, is it the same way?

The HVAC fan operates independently from the AC compressor. The compressor is variable speed.

 

[Big Earl]

The HVAC fan operates independently from the AC compressor. The compressor is variable speed.

Adding to that, a high fan speed with fresh air can create higher load on the system because you are essentially heating/cooling the outside. Conversely, a low fan speed will limit the amount of work the system can do. Fan speed, system performance and efficiency are all related. Automatic mode offers a pretty good balance between fresh air, recirculated air and fan speed.

 

[Swoosh99]

Yeah these trips just have high overhead from initial heating or cooling transients. Also combining that startup transient with slow speeds does not help. It is avg wattage/speed that you calculate to give you Wh/mi…

All that battery cooling from short drives makes sense why I'm losing range. I own a leaf as well, which seems to do better in the city. They don't cool the batteries tho, I guess this is a trade-off between losing range vs battery degradation.

Do you know how accurate the Tesla is able measure their battery charge? I assume that they are just measuring changes to the battery's voltage over time but battery voltage does not deplete linearly so it seems that they could get inaccurate readings when reporting the remaining battery from time to time.

 

[AlanSubie4Life]

Do you know how accurate the Tesla is able measure their battery charge?

I think it is very accurate. I don’t see any evidence it is ever worse than about 1-2kWh off from the actual SoC in most vehicles. It’s important to be accurate otherwise the vehicle would shut down prematurely and that just has not been happening. (There is a 4.5% buffer below 0%, so I think that likely gives you a HIGH upper limit for how bad they think the estimation can be - there are other reasons for the buffer too, so I don’t think Tesla thinks their estimation can be off by 4% of the full battery capacity).

 

[jcanoe]

All that battery cooling from short drives makes sense why I'm losing range. I own a leaf as well, which seems to do better in the city. They don't cool the batteries tho, I guess this is a trade-off between losing range vs battery degradation.

Do you know how accurate the Tesla is able measure their battery charge? I assume that they are just measuring changes to the battery's voltage over time but battery voltage does not deplete linearly so it seems that they could get inaccurate readings when reporting the remaining battery from time to time.

You can help the Tesla vehicle to re-calibrate the battery management system. Charge the battery to 95% or higher, then drive until the battery state of charge drops to 30% to 20%.) Repeat at least two additional times over the following days. Also,turn off Sentry Mode when the Tesla vehicle is parked at your home or work location. The Tesla vehicle needs to periodically measure the open cell voltage of the cells within the battery. This requires that the Tesla vehicle disconnects the battery from the vehicle as when the Tesla vehicle enters sleep mode. Whenever Sentry mode is active (Summon mode too) the Tesla vehicle does not enter sleep mode.

 

[Swoosh99]

You can help the Tesla vehicle to re-calibrate the battery management system. Charge the battery to 95% or higher, then drive until the battery state of charge drops to 30% to 20%.) Repeat at least two additional times over the following days. Also,turn off Sentry Mode when the Tesla vehicle is parked at your home or work location. The Tesla vehicle needs to periodically measure the open cell voltage of the cells within the battery. This requires that the Tesla vehicle disconnects the battery from the vehicle as when the Tesla vehicle enters sleep mode. Whenever Sentry mode is active (Summon mode too) the Tesla vehicle does not enter sleep mode.

Thanks, do I need to drop it from 95% to 25% within a couple days or can it be done over a week or two to be effective? It's not as easy for me to run it down that much unless I take it around the island.

 

[jcanoe]

Thanks, do I need to drop it from 95% to 25% within a couple days or can it be done over a week or two to be effective? It's not as easy for me to run it down that much unless I take it around the island.

You can charge and the discharge the battery over as many days as you need. The problem is that when the battery is maintained within a very narrow state of charge, i.e. 50% to 60% the Tesla vehicle's battery management system does not have enough data to accurately estimate the state of the battery at the extremes.

 

[CpYledomUser1]

I am having a really hard time relating wh/mi to some sort of efficiency rating. Basically I have no idea if I’m being efficient and by how much. Currently my MY shows an average of 256 wh/mi, it’s a 2022, if that matters. How does that relate to MPG or MPGe?

 

[jcanoe]

I am having a really hard time relating wh/mi to some sort of efficiency rating. Basically I have no idea if I’m being efficient and by how much. Currently my MY shows an average of 256 wh/mi, it’s a 2022, if that matters. How does that relate to MPG or MPGe?

It can be confusing when trying to relate Watt hours per mile (Wh/mile) to something more familiar such as miles per gallon (MPG) or MGE equivalent (MPGe) an even more difficult to understand measure.

First, know that 256 wh/mi is efficient EV driving (a lower Wh/mi value is more efficient than a higher value.) Some Tesla Model Y drivers report overall Wh/mi at around 240 Wh/mile but 270Wh/mile seems to be a typical result for many Model Y drivers, even a bit higher (especially in winter.)

To convert Wh/mi into miles per kWh:

First, divide the Wh/mi by 1000: 256Wh/mi/1000 = .256kW/mi

then. divide 1 by the .256kW/mi: 1/.256 = 3.9 miles per kWh.

(For comparison 4 miles per kWh is 250Wh/mi which is quite good efficiency. Using Tesla's numbers the Long Range Model Y's efficiency is 4.2 miles per kWh or 238Wh/mi. Generally to meet or exceed the Tesla's stated efficiency number you would have to drive no faster than 45 or 50 MPH and turn off the climate control system.

So what about MPG? The EPA rated combined city/highway efficiency of the 2022 Long Range Tesla Model Y MPG equivalent (MPGe) is 125 MPGe. MPGe calculations make assumptions about the price of 1 gallon of gas and also the cost of 1 kWh of electricity. MPGe includes charging overhead and charging losses.

Fueleconomy.gov, 2022 Tesla Model Y

To get in the ballpark of the EPA MPGe value take 33.7kWh (the number of kWh in a gallon of gas) and multiply this by your Wh/mi (after converting Wh/mi converted to miles per kWh). 33.7 X 3.9 = 131 MPG; then assume 5% overhead and charging losses (just because) and you get 125 MPG. Your 256Wh/mi result is right at the stated efficiency.

 

[sleepydoc]

I am having a really hard time relating wh/mi to some sort of efficiency rating. Basically I have no idea if I’m being efficient and by how much. Currently my MY shows an average of 256 wh/mi, it’s a 2022, if that matters. How does that relate to MPG or MPGe?

It depends what your goal is. MPGe is intended as a rough comparison of the amount of energy in gallon of gasoline. (You can find an explanation here.) There are also online MPGe calculators.

If you want to do a comparison and calculate “MPG” based on current costs, the formula is:
1000 * Fuel cost ÷ ( wh/mi * Electric cost in $ per kwh)

Example: In the summer I average 250 wh/mi. It costs me $0.06 per kwh to charge and gasoline is $3/gallon.

1000* 3 ÷ (250 * 0.06) = 200 MPG​

i.e. It costs me the same to drive my Model Y as it would for a car that gets 200 MPG.

 

[CpYledomUser1]

Hey, thank you. I know we all have range anxiety but I have it the other way, too. Having driven a Prius for 13 years, it’s kind of ingrained in me to try and maximize efficiency. 125 mpg is a massive improvement even over best case scenario in a Prius though. Best we ever got out of that was 56mpg, and we have t seen that in quite a while.

 

[sleepydoc]

Hey, thank you. I know we all have range anxiety but I have it the other way, too. Having driven a Prius for 13 years, it’s kind of ingrained in me to try and maximize efficiency. 125 mpg is a massive improvement even over best case scenario in a Prius though. Best we ever got out of that was 56mpg, and we have t seen that in quite a while.

Now, just to increase your anxiety, take the amount of CO2 produced per kWh into account!

 

[jcanoe]

Hey, thank you. I know we all have range anxiety but I have it the other way, too. Having driven a Prius for 13 years, it’s kind of ingrained in me to try and maximize efficiency. 125 mpg is a massive improvement even over best case scenario in a Prius though. Best we ever got out of that was 56mpg, and we have t seen that in quite a while.

Now the bottom line. Unless you charge at work or some other location where someone else pays for the electricity you are probably paying about $5 or a little more for a gallon equivalent (33.7kW) of electricity when you charge at home (Supercharger costs are even higher.) If gas costs you $3.20 per gallon and you achieve (best case) 56 MPG in your Prius your cost per mile (just for gas) is 5.7 cents per mile. The cost per mile of driving the Tesla Model Y would be $5/125MPGe or 4 cents per mile. Many conventional (non-hybrid) internal combustion engine (ICE) vehicles such as trucks and SUVs never get anywhere near 30 MPG let alone 56 MPG, typically not much over 20 MPG. At $3.20 per gallon for gas driving a conventional ICE vehicle that achieves 22 MPG would cost 14.5 cents per mile.