Join Date: Dec 2018
Location: Monte Sereno, CA
I also noticed some time ago that the reported efficiency did not seem to match my rough calculations, so I decided to do a data analysis the old fashioned way: measure how much total energy I put into the vehicle over a long period and then divide it into the number of miles I drove over that period. I used the report from my ChargePoint home charger, which is the only charger I have ever used, to determine the total amount of energy I put into the vehicle. Then I simply divided the number of miles driven over the same period by the total energy. In my case, I chose April 16, 2019 as my start date and August 23, 2019 (yesterday) as my end date. During that period, I put a total of 1,361.4 kWh into my I-Pace. Over that period, according to the Jaguar InControl app, I had driven 2,760.9 miles. The simple math is that my efficiency was 2.03 mi/kWh. There will be a slight error in this calculation because my battery was not 100% full on April 16, nor is it full now. The ideal calculation would start and end at 100%, but it is still quite accurate.
So, how does this compare with what the car tells me? Using the InControl app, you can easily calculate the amount of energy reported by the car per trip. I assume the app reports the same number as reported on the display in the car, but I don't know that for sure. If you divide the miles reported for each trip by the mi/kWh reported for each trip, you will get the kWh used on each trip as reported by the app. In my case, over the same period as I used above, the total energy used was 1,103.9 kWh - clearly a lower number than what ChargePoint tells me I put into the battery. In fact, it is off by 23.32%. This is a smaller error than reported by sciencegeek, but still clearly significant.
My typical driving mission, for your comparison purposes, is around the San Francisco Bay area in a combination of city and highway driving. I typically drive 70-80 mph on the freeways and close to the speed limit when possible on surface streets, however quite a bit of time is spent in stop/go traffic on freeways and city streets. I would estimate about 25% of miles are in stop/go traffic and 75% is at high speed on the freeway. However, if you look at time spent, it is probably more like 60% in stop/go traffic and 40% at high speed. Temperature here since April has averaged between 60 and 90 deg F. and I use AC always set at 72 in the car. Some statistics accumulated from InControl are below:
Average trip length: 11.04 mi
Total miles: 2,760.9
Total energy reported by InControl: 1,103.9 kWh
Total energy reported by ChargePoint: 1,361.4 kWh
Total regeneration reported by InControl: 304.7 kWh
Average efficiency reported by InControl: 2.50 mi/kWh
Average efficiency calculated using ChargePoint data: 2.03 mi/kWh
Note that I assume that the InControl app is taking regeneration into account when it reports energy used per trip. If not, then the reported efficiency is off even more than my calculations state. I intend to keep tracking the data over the first year of ownership and then again in a few years to see if there is any degradation in efficiency over time.