Found out today, the Wh/mile number changes at the .5 mark!

[timk225]

Over this past summer, my lifetime Wh/mile decreased from 257 to 251. It would have fallen more if not for my weekend early morning maniac speed runs to work to try and break the 18 minute mark. (Record was 22.5 miles in 18:13, thanks to every idiot on the road getting in my way. CALM DOWN WHINERS, these speed runs only happened at 6 AM on Sat and Sun mornings, when there was little to no traffic). But during October, I spent some time trying to drive carefully and get my Wh/mile down to 250 for no good reason. But even though I'd use my calculator on my phone to do the KW/miles calculation, and got down to 250.98, the displayed Wh/mile never dropped below 251.

Today, I was driving somewhere, and wanted to see my total miles driven, so I scrolled up the odometers to see the bottom one and it was at 252!

Just then, I regenned down a hill, and it dropped back to 251! I was right on the edge! I spend the next few minutes doing hard accelerations then regens to make it go from 252 to 251 to 252 to 251 to 252 to 251. Then I got out my calculator and ran the same KW / miles calculation, and it showed 251.509-something.

So that proves it, the Wh/mile would only go from 251 to 250 when I got the average down to 250.499, not 250.999.

So now you know that!

 

[evM3Sekar]

I figured something like that based on "Since last charge" data back in summer. They should report Wh/mi with a significant digit after the decimal point.

Likewise Tesla should include one significant digit in KWh usage under "Since last charge" - after all they do it for mileage reported there. The two trip meters could be over a long time, so it doesn't matter as much - one significant digit as in 3.7 KWh makes more sense than in 5376.2 KWh (you almost need MWh as unit here).

 

[earthwormjim]

Nearly every measurement metric in the car performs rounding and not truncation. The cars have a powerful processor with actual floating point hardware, so there's no need to do integer math or truncation.

You can see it on the trip display graph for percentage of battery charge left when navigating somewhere.
When the graph shows XX.5% (by eyeballing where the graph line is), the total charge percentage at the end of the trip will be rounded up to XX.0% + 1%. The opposite occurs if it is XX.4999%, the end of trip number will show XX.0% - 1%.