Today I used my Model X to tow a golf cart on a utility trailer about 110 miles. The trip was a bit of a torture trip for towing since it started in 89 degree heat and went up about 4,000 feet in elevation right away up a mountain road with switch backs. Then a longish up and down route of 55 to 60 mph highway driving, then 70 mph freeway driving. Attached is a picture of what I was towing, and what the trip meter looked like at the end ... I rolled in with 6 miles of range remaining! This trip normally uses about 130 rated miles. With the trailer, it used 240 rated miles. From looking at the energy graphs while driving, it seems the biggest range penalty was due to speed, not climbing. Climbing up the mountain had me going around 30-40 mph, and while energy usage was high, it was higher when I got onto the highway and was driving 60 mph. At one point, the last 30 minutes was averaging 980 watts per mile. The freeway was really bad too at 70 mph. If I had been worried about range, I would have throttled it back down to 55 mph and saved a lot of range. This particular utility trailer no doubt acts as a big wind break. I estimate that the trailer and load weighs just under 1,000 pounds. The other thing I was wondering about is how the car cooling system would handle the extra load. Well, the heat and pulling load and full AC didn't seem to bother it a bit. No power limiter came on. The X felt a little heavier pulling the trailer, but it still had plenty of torque and pickup.