Ok just did the first part of a trip. We were off because of the rain by a little bit the model 3 was way off. The 265wh/ mi was way off as an estimate.
We got that on the mainly flat super highway but with more load it was wrong and rain and then going they the mountains. It looks like fitting against teslafi.com actual, it is more like 285 Wh/mi which is still less than the nominal 295 estimate for performance model 3.
What I’ve found is that the estimates for the P3D are pretty good for flats and highways, but very far off when there are hills and things. But more like 275 Wh/mile is accurate for highways.