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Discussion Starter #1
From the lifetime electric miles, total miles, and, lifetime mpg stored in the car, I can compute the lifetime gasoline used. At least if the display shows what I think it shows. So, taking total miles - electric miles gives me gas miles. The car has a "useless" MPG display, which I am guessing is total miles / total gallons. So, that would say that total gallons used should be total miles / lifetime MPG. But this seems to be off. I have not used a tank yet, and, that computation is showing more gas used than I think I have used (based on 2 gas trips and what the display said my gas usage was for each of those, at least my memory of those!). Should the formula I have be correct, or, is that just a guess really, perhaps the car can't really accurately measure gas used and thus the lifetime MPG is a suspect number?

I was hoping to be able to compute lifetime kWh used, I don't see it on the display anywhere, and, it's not in the MyChevy app. Seems like there should be a way to take the lifetime MPGe and calculate the lifetime kWh. This is more for figuring electric usage at home and other planning purposes. Is there a way to use MPGe to calculate lifetime kWh used on the card end? I am not sure what MPGe as calculated by the car represents.
 

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Your gas used formula is correct "Total miles / Lifetime MPG". Not sure if there is a way to calc kWh used.
 

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Discussion Starter #3 (Edited)
Seems like this should be possible. I have read that MPGe = 3370 / kWh per 100 miles. So, on my last electric trip, I went 39.2 miles on 8.5 kWh. So, kWh per 1 mile = 8.5 / 39.2 = .2168 times 100 for 100 miles = 21.68 kWh per 100 miles. So, it should be 3370 / 21.68 but that equals 155 MPGe. However, the display for the trip shows 129. So, I am missing something here. Not sure what!? If I can get that formula right, then, I can use MPGe and miles to figure kWh used.

Ok, so, I have used several trips, and apparently, I can do this:

(Miles traveled * 33.7 * .83) / kWh used = MPGe

So, in my example above, that's 155 * .83 (must be the charging energy lost) = the 129 the display shows. This seems to hold true on every trip I have recorded.

So, this means, kWh used = (Lifetime Miles traveled electric * 33.7 * .83) / Lifetime MPGe

So, now the trick is to figure out the lifetime MPGe for electric only. Since there is a combined MPGe, the next step is to leverage that and figure out how it is calculated, anyone know how combined MPGe is calculated? Using that, I should be able to backtrack into Lifetime MPGe for electric only. Unless it's in an app or display somewhere?
 

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Seems like this should be possible. I have read that MPGe = 3370 / kWh per 100 miles. So, on my last electric trip, I went 39.2 miles on 8.5 kWh. So, kWh per 1 mile = 8.5 / 39.2 = .2168 times 100 for 100 miles = 21.68 kWh per 100 miles. So, it should be 3370 / 21.68 but that equals 155 MPGe. However, the display for the trip shows 129. So, I am missing something here. Not sure what!? If I can get that formula right, then, I can use MPGe and miles to figure kWh used.
Your kWh per 100 miles is taken from to small a sample size. You would need to keep track each day for at least a year that would give you an average of all types of driving conditions. What you did would be like taking 1 gallon of gas driving until it is gone and saying I went X miles then extrapolating that which would be bogus.
 

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Discussion Starter #5 (Edited)
But that is not at all what I am trying to do. I am trying to take the numbers Chevy provides, and, calculate the missing number. I am wanting to take lifetime numbers and come up with a close estimate of how many kWh were used over the life of the car, and I believe that is possible if I knew the formulas Chevy uses, which I am trying to deduce. They calculated 129 MPGe, it is based on some formula. They tell me I used 8.5 kWh, and they told me it's 39.2 miles, so, the math is correct I believe.

I just have to figure out how they calculate combined MPGe, and if I knew that formula, I could compute what I want to compute. Which will be an estimate of course, but, pretty close.

First step is to make the numbers match on the display and calculate as they do. That is what I am trying to do.

I don't want to track each day, I want to be lazy and use the lifetime totals to figure the kWh used. Form there, I can add in the charging loss and see how it matches up against electric used and what I use per year.

So, my question is merely how to compute the combined MPGe as Chevy does. If someone knows, please let me know. If I had that, I can figure exactly what I want.
 

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Here is the combined formula:

MPGe = (Miles Electric + Miles Gas) / (Gallons of Gas + (kWh / 33.7 * 1.2))

For the life of the car, the odometer will give you (Miles Electric + Miles Gas). If you have kept track of the gallons of gas used you should have everything you need to get total kWh over the life of the car. Then if you multiply the result by 1.2 (charging efficiency) it will give you the kWh that you used from the electric grid.
 

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Discussion Starter #7
But I don't need gallons of Gas as I can compute that as Lifetime Miles / Lifetime MPG = Lifetime Gallons used. I had just figured out your formula right after you posted it but before I read it, thanks though as it confirms what I figured. Therefore, by just using numbers GM gives me and without careful tracking, I can compute lifetime gallons used and lifetime kWh.
 

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Seems like this should be possible. I have read that MPGe = 3370 / kWh per 100 miles. So, on my last electric trip, I went 39.2 miles on 8.5 kWh. So, kWh per 1 mile = 8.5 / 39.2 = .2168 times 100 for 100 miles = 21.68 kWh per 100 miles. So, it should be 3370 / 21.68 but that equals 155 MPGe. However, the display for the trip shows 129. So, I am missing something here. Not sure what!? If I can get that formula right, then, I can use MPGe and miles to figure kWh used.

Ok, so, I have used several trips, and apparently, I can do this:

(Miles traveled * 33.7 * .83) / kWh used = MPGe

So, in my example above, that's 155 * .83 (must be the charging energy lost) = the 129 the display shows. This seems to hold true on every trip I have recorded.

So, this means, kWh used = (Lifetime Miles traveled electric * 33.7 * .83) / Lifetime MPGe

So, now the trick is to figure out the lifetime MPGe for electric only. Since there is a combined MPGe, the next step is to leverage that and figure out how it is calculated, anyone know how combined MPGe is calculated? Using that, I should be able to backtrack into Lifetime MPGe for electric only. Unless it's in an app or display somewhere?
Divide your MPGe figure by 1.2...which I believe is a "loss" factor...155/1.2 = 129.2.

I personally believe 1.2 is too large and losses are less than that.
 

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Discussion Starter #9
So, using numbers that the display and the MyChevy app gives you, here is the resulting formula. We compute virtual gallons used as (Lifetime Miles / Lifetime Combined MPGe) - (Lifetime Miles / Lifetime MPG). These are all numbers Chevy gives us. Now that we have virtual gallons, we can convert to vehicle kWh used. Car kWh used = virtual gallons * 33.7 / 1.2. From there, you can apply whatever factor you want or have measured for charging loss and compute electricity you have used to charge the car over it's lifetime. Chevys numbers already used 1.2 so we have to here. But we can take the vehicle kWh consumed now and apply the factor we believe is correct for our charger. This works now only for every trip I have recorded thus far, but, the total as well. Unless I made a typo here. This works for the gen2, no idea about the gen 1 or what info that car provides or if the Chevy formulas are the same or not.
 
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