miles/kWh usage MID; is it even withing the ballpark guestimate?

Yep, that estimate is probably good for the segment of your trip you actually was on EV mode. I think the key point is that you did regen on downhill, and probably did not use much EV mode after that. In your case this happened unintentionally, but I have done similar thing intentionally to get daily EV mode Average miles/kWh that looked like below. See the number on July 31 is 99.9 miles/kWh. And this number despite the fact I actually drove total 36.6 miles on that day. But you see the Average MPG was lowish 73.7.

I did this probably when I had very little EV range left on my car on that day similar to you forgetting to plug in. So, I could not make a good use of short EV range for the 37 miles trip I did. I drove most of the trip on HV mode using gas, then switch to EV mode only when the car was in descent on the downhill. During the descent, the miles/kWh will remain 99.9 which is the max number that can be displayed, similar to 999.9 mpg on the gas side. I probably completed the entire trip doing this just to gain EV range by regen to charge the traction battery. The result is that I ended up gaining EV range when I came home by using gas engine, very similar to CHG mode.





That was the extreme case in that EV mode was on only during regen segment and never used for the propulsion. But if you did long enough regen and after that did not drive much on EV mode, then it is possible to get daily miles/kWh wildly high like shown below. Again for those cases I was driving mostly on HV mode, so overall efficiency was no where as good as driving longer distance on EV mode only. In my case, at that time I was using this technique, the gas was way cheaper than electricity. So it ended up using more gas but overall saved money and overall mpg stayed about the same with average EV efficiency showing ~8 miles/kWh.

 

To sort it out, you need to know the following

1. What EV range (or SOC %) at the beginning of the day?
2. How did you switch in and out of EV mode during the day?
3. If you know, what distance did you drive on EV mode?
4. At the end of the day what SOC% was left? (we already know you used up all the SoC by the end of the day)

Yeah, if you had a full charge at the beginning of the day and drove the uphill on EV mode and used up the entire SOC on that day, then it is very unlikely you will see 29miles/kWh on the Daily Eco log. But, if you had only 15% SOC at the beginning of the day. And you drove most of the day on HV mode and switched to EV mode at the very end of your trip on regen and at the finish on a mostly flat road for a few miles until you deplete the SOC. This can end up with 29miles/kWh on the Daily Eco log. Remember any regen on EV mode will be calculated as infinity even though the number max out at 99.9miles/kWh. The longer you had regen EV mode and less EV mode you drove after the regen, you are likely to get a very high daily average. Without knowing how you drove on EV mode on that day, it would be impossible to figure out how the number was generated.

 

BTW, if you need to estimate your EV efficiency to calculate the breakeven point for EV vs HV, then you should not be looking at the daily Eco log data. The daily number fluctuates too widely as in your own case. You only need to pay attention to the lifetime EV efficiency shown on the Drive Monitor 2 shown below. The EV efficiency on DM2 is for since the reset. If you have not reset the data, then it is for the odometer reading. I am certain that your single day of 29miles/kWh daily record did not change the value on the DM2. Say single 4 miles of EV mode drive with 29miles/kWh efficiency over the duration of odometer have almost no effect on the average efficiency.

 

Yeah, your answer is in line with that you had very little EV range (SOC %) in your car on that day. What I find strange is that if you did not "manually" switch between EV and HV mode, then all of the EV range should be totally gone after starting the car and driving a few miles. My suspicion is that you had a very long downhill on your way back home near very close to your home? That would regen the EV range depleted traction battery back to EV mode with a few % of SOC showing. Depending on that long regen distance where the car would calculate it as infinity distance/kWh, I can see a scenario that by the end of the day, you have the high number of miles/kWh.

Just to prove my theory, can you check the Eco Diary entry of the June 3 for Distance miles and Average MPG as my example of the second photo image on #2 comment. You said you have never seen that screen before. You must toggle the EV efficiency screen you are seeing to other records (two monthly records and one daily miles/mpg record) by pushing the wheel enter button. If my theory is correct, your mpg should be lower than similar drive you have done with a full EV range.