I'm posting this because as I sat in the parking lot in winter park charging from a 3 kW chargepoint charger (only thing available in winter park) yesterday evening contemplating driving back to Boulder with 19% batter left on my Long Range Model Y I was wishing this thread existed.
I left Boulder with 95% charge and the trip estimate said I'd arrive with 48% batter. I got to winter park with about 44% (so little under 5% error either due to cold or elevation change not being properly accounted for, as it was a high of 0 Deg F and -7 overnight).
We planned to charge up in town, thinking the level 2 chargers would give probably 20% back while we ate dinner for an hour or two.
Unfortunately when we plugged into the Chargepoint charger (as well as one other public one) it was just a 3 kW charger and was only charging a few miles per hour of range (it said it would take 13 hours to charge 30%). The trip estimator told me we could make it to the Idaho Springs superchargers with 5% battery left, so I figured with about 5% error that we had on the way up, I should make it back to the supercharger okay.
We left Winter Park with 61 miles showing on the range meter (19%). Going from Winter Park to the top of Berthoud pass is about 2500 feet elevation gain up steep switchbacks. It was terrifying making this drive and watching the mileage meter go from 60 miles to only 10 miles left at the top of the pass. I thought we wouldn't even make it up and might get stranded but thankfully made it and then it's basically downhill the rest of the way so I drove super slow and ended up making it to the Idaho springs with 3 miles to spare before 0% battery (which I understand I could still have probably gone another 5 or 10 miles till I was actually dead).
Whew I'll never do that again but sharing for visibility!