The trailer goes on: the first towed miles, at 1.6 mi/kWh

Day three is the hinge of the trip. Everything before it was the control: two days and about 800 miles of empty Rivian R1T up I-15, holding right around 2 mi/kWh across the desert, dropping to 1.87 on the climb into Utah and touching 3.38 on the descent into Salt Lake. Clean baseline, no trailer.

The morning started with one last empty top-off at the Sandy Rivian Adventure Network, conveniently a hundred yards from the U-Haul depot. Trip A read 7,289.3. Then the enclosed U-Haul cargo trailer went on the hitch, Trip B got reset to zero, and the whole character of the trip changed. The first twenty miles run with the trailer empty; then the 2025 Ducati loads and it is a fully towed rig for the drive home.

Here is why this trailer is interesting. It is a U-Haul 5x8 enclosed cargo trailer, about 1,000 pounds empty, inside dimensions 8 feet 1 inch long by 4 feet 8 inches wide by 5 feet tall, rated to 1,800 pounds of load and 2,700 pounds combined. The Ducati with all its parts adds roughly 400 pounds, so loaded the whole rig is only about 1,400 pounds, a fifth of the 6,000-pound Airstream. But a light trailer is not a low-drag trailer: an enclosed box presents a large flat front, somewhere around 28 square feet, so at highway speed the range hit comes mostly from pushing that air, not from the weight. That is exactly the variable a motorcycle on an open rail would hide, and it is what makes this a clean aerodynamics test against the empty baseline.

About twenty miles southeast of the charger, near Alpine, the reason for the whole trip was waiting in a driveway. A 2025 Ducati Panigale V4 in the green, white, and red tricolore livery, bought on Bring a Trailer and now ours to bring home. It went up the ramp and got strapped upright inside the enclosed box, spare parts boxed beside it, and the doors came down. Trip B, which had rolled its first stretch with the trailer empty, now carried the full load.

And the first number is in, three ways that agree. The leg from Sandy south to the Beaver creamery, the same charger we stopped at on the way up, read 195.0 miles on 123 kWh by the Trip B segment counter: 1.59 mi/kWh towing. The continuous Trip A odometer, 7,289.3 to 7,484.3, corroborates it at 1.61, and the Rivian’s own towing screen put the U-Haul profile at 1.6 mi/kWh. Empty, that same truck held right around 2 mi/kWh. So the enclosed trailer costs roughly a fifth of the range.

Then the towing screen threw out a number worth a footnote. It read the trailer’s current weight as 2,500 pounds. The rig really weighs about 1,400. But that is not a scale reading. The Rivian estimates trailer weight once, at park-exit when towing starts, from how hard the motors work to pull away, and grade skews it: uphill it reads heavier, downhill lighter. So the 2,500 is not reality, it is a snapshot of how hard the truck thought it was working the instant it started rolling. An interesting data point, and a reminder that with a boxy trailer the truck can feel the load as bigger than the scale says, because at highway speed the thing it is fighting is the drag, not the weight.

One paid Tesla splash in Nephi kept the loaded truck in range between the free Rivian stops, 18.82 kWh for $7.52, the first time the tighter towed range broke a clean streak of free charging. The motors ran warm the whole way, 136 degrees, working against the drag. One leg is not the whole story, and the numbers will firm up on the run home, but the shape of it is already clear: light does not mean low-drag, and an enclosed box is the expensive kind of trailer to tow.

By dusk the rig was down out of Utah and across the Arizona strip into Mesquite, Nevada, a second towed leg of 142.5 miles behind it. And here the terrain flipped the number the other way: where the climb to Beaver cost efficiency, the long drop through the Virgin River Gorge, better than 4,000 feet of it, handed some back. That leg ran about 1.70 mi/kWh towing, up from 1.59 on the climb, the regen clawing back on the descent what the grade took on the way up. Trip A closed the day at 7,626.8 miles, 337.5 towed miles from Sandy at roughly 1.65 mi/kWh overall. Parked at a hotel for the night, Ducati still in the box. One towing day down, and the run home just getting started.