I added another six lines of data to the spreadsheet. The last five represent our weekend road trip from just north of Denver to Taos, NM, and back: about 700 miles of mountain and valley driving, including one big, wet snowstorm in southern Colorado and northern New Mexico. We made only one Supercharger stop, at Silverthorne, outbound. The rest of the charging was accomplished using a 40A 14-50 at the Monte Bello RV Park in Taos and a 70A L2 charger at Wood's High Plains Distillery in Salida, CO (thanks to Cottonwood for donating the charger, and to PT Wood for hosting it).
Our highest usage came on the first leg, Broomfield to Silverthorne, at 406 Wh/mi, but that's because it was driven at relatively high speeds and ends 3582 ft. higher than it starts. The lowest usage came in at 252 Wh/mi on the second leg, from Silverthorne to Salida; the net elevation change of -1886 ft. being the main contributor. The Salida to Taos leg was dominated by a worsening winter storm that had us feeling our way on an unplowed highway with as much as six inches of snow and slush and near whiteout conditions at times; we were happy to make it to Taos with 30 Rated miles remaining having started with a theoretical 70 Rated mile cushion. Two days later, returning from Taos to Salida the roads were clear, but the temperatures dropped into the single digits F.; we actually managed to beat the Trip predictions by one percent by again driving conservatively. The last leg featured a howling crosswind off the port bow through South Park (yes, that South Park); we started with an 18% cushion, of some 46 Rated miles, and were able to drive at or above the speed limit the entire way, knowing that our next stop was an overnight charge at home (we 'gave away' about 3% of the 18% cushion between the higher speeds and the strong winds).
The main takeaway from the experience is how useful the new Trip tab in the Energy app can be, as an aid to planning a charge and then monitoring your progress over the course of a leg. The largest deviation we encountered was of -13%, on the leg from Salida to Taos: the Trip graph showed we would need 70% of a full charge while we ended up using 83%. Most of the loss against prediction came in the last sixty, snowy miles of that 170 mile leg; but we knew the weather was deteriorating ahead of us and drove conservatively for the first hundred miles, matching or bettering the predicted usage until the snow started to pile up in earnest.
Using EVTripPlanner.com for that snowy leg, inputting a speed factor of 1.2 (while we actually drove at a speed factor of about 0.9) and using conservative settings for OAT and climate control, the predicted usage of 205 Rated miles was only slightly more optimistic than the actual 215 Rated miles used.
Overall, the trip was safe and uneventful, even through the worst winter conditions I've driven in some years: the P85D handles wintry driving conditions with unshakable aplomb. We never felt that we were driving at the edge of disaster, even with the left tires riding in a traffic rut and the right tires riding in six inches of fresh, heavy snow. The Sub Zero features were much appreciated, particularly the heated steering wheel: with adequate defrosting of the windows, and warm hands and backsides, we were able to run with the cabin temperature set as low as 64-65º, in comfort.
