Denver to Yellowstone: A Side-by-Side Simulation

Denver, Colorado to Madison Campground, Yellowstone National Park. It is an ordinary trip — a plausible first leg of a summer holiday for anyone in the Front Range — and it happens to cross some of the thinnest charging country in the lower 48.

The destination was not chosen to be unfair. It was chosen because it is typical: Madison has 278 sites, no electrical hookups, no water hookups, no sewer hookups, and no gas station. Generators are permitted only between 8 a.m. and 8 p.m. under a 60 dB limit. Whatever energy the trailer needs on arrival, it has to bring with it.

Wyoming's charging reality shapes this. Reporting on the state's network notes that apart from Jackson and Riverton, most Wyoming charging sites sit along I-80, I-25 and I-90 — leaving large gaps in rural areas — and most are Level 2 rather than fast chargers. A cautious electric driver might route via I-80 and Rock Springs instead, which adds about 30 miles and roughly matches on time. The simulation below gives the electric rig the shorter route and assumes its fast chargers all work.

Before either rig turns a wheel there is a structural fact that decides most of this race, and it is not about the tow vehicles.

The rig has two batteries. The truck's fills from a DC fast charger at 150 to 350 kW. The trailer is equipped to do the same — LightShip's published specification is a NACS port supporting both AC and DC, with a peak of about 155 kW and a 10–80% DC charge in roughly 42 minutes. On paper the two halves of the rig fill at comparable rates.

The gap between rows two and three is roughly nineteen to one, and which row applies is decided not by the trailer but by whose logo is on the charger.

The trailer's house loads run continuously in transit — refrigeration, twelve-volt systems, and a thermal plant that cannot be switched off, described on Trailer Load & Thermal. Taken at 0.7 kW, they draw roughly 9 to 10 kWh across this trip.

That has a consequence the finish rules make sharp: a trailer charged at home and then towed all day arrives at about 87%, not 100%. It cannot meet the finish condition on departure charge alone. And topping it up early does not help — it simply depletes again over the remaining legs. The top-up has to happen at or near the final stop, which means it is serial time at the end of the day rather than something absorbed into an earlier break.

Unless, of course, it is being charged continuously while driving. That is the one arrangement under which the question does not arise.

Two configurations are run, because the answer depends heavily on pack size. The Rivian R1T Max Pack is the vehicle most associated with electric-trailer ownership. The Silverado EV RST carries the largest pack available on a pickup and represents the best case currently purchasable.

Published towing data puts the range loss for a mid-size trailer at 40–60%, with Rivian's own engineers citing about 50% at full rated tow. The simulation uses 45% — the favourable end — on the grounds that the AE.1 is unusually aerodynamic for a trailer. Owner practice for this class of rig is described as legs of 90 to 130 miles between fast charges, which brackets the 115 mi figure above.

At the final stop the trailer needs roughly 9 to 10 kWh to reach 100%. What that costs depends entirely on the question from section 02.

• Supported DC at that stop: about 20 minutes, running in parallel with the truck's own 80→100% taper. Costs the rig nothing.
• AC fallback: about 80 minutes at 8 kW net of house load. Adds roughly 50 minutes beyond the truck's charge.

West Yellowstone is the last practical opportunity, fourteen miles from the campground. It has Level 2 at several hotels and the KOA, and eight Tesla Superchargers at the Grizzly & Wolf Discovery Center — whether the trailer can use the latter is precisely the open question.

The gasoline-hybrid rig has a duller run, which is the point.

617 miles on 518 miles of range means one refuelling stop, roughly ten minutes at a pull-through lane. The finish rule requires arriving with a full tank, so a second ten-minute top-off happens at West Yellowstone, fourteen miles from the campground. Twenty minutes of stopped time in total.

The trailer needs no stop at all. Over 10.9 hours of driving the umbilical delivers roughly 55 kWh net of house loads — far more than the 9 to 10 kWh the trailer actually consumes. It arrives full because it was never allowed to fall.

Fuel: about 43 gallons for the trip, of which roughly 8 gallons is attributable to charging the trailer.

Driving time is identical for every row; nobody drives faster. The entire difference is stopped time.

Two things are worth reading out of the spread. First, pack size matters more than badge — the Silverado EV's larger pack removes two stops relative to the Rivian, a bigger effect than anything else in the table. Second, network support for the trailer is worth about 50 minutes, and it is the one variable here that is neither a property of the trailer nor of the truck. It is a business-development question that lands on the owner as elapsed time.

The AE.1 carries a motor on its own axle. It propels itself, reducing load on the tow vehicle and extending the truck's range — LightShip describes it as delivering up to double the range and efficiency on longer routes, and for an electric rig short on range that sounds like exactly the tool for the job.

Whether it helps or hurts a door-to-door time depends entirely on the section 02 question, and in one of the two cases it hurts badly.

The mechanism is the fill-rate asymmetry running in reverse. Without network support, trailer assist moves energy demand out of a tank that fills in twenty minutes and into one that fills in seven hours. The feature that exists to reduce charging stops can, in the wrong place, become the largest single time cost of the trip.

This is worth stating carefully, because it is not a criticism of the trailer's engineering. The hardware is not the constraint — network validation is. As compatibility broadens, this finding moves from the second case toward the first.

And it inverts entirely on the gasoline rig. With a source replenishing the trailer while driving, trailer assist costs no stopped time in either case, and the question becomes purely one of fuel and thermal load. That arithmetic is not flattering either, and it is on the Roadmap.

A simulation is only as honest as its assumption list. Every judgment below was made in the electric rig's favour.

It measures elapsed time, because that was the rule. That is one objective function and not everyone's.

An owner who enjoys the stops is not paying a four-hour penalty — they are getting four more hours of a trip they wanted. Charging stops in Wyoming land in Casper, Riverton, Dubois and Jackson, which are not bad places to spend forty minutes. If the journey is the point, this entire page measures something you are not optimising for.

It also does not measure cost, emissions, noise, or how any of this feels. The gasoline rig burns about 43 gallons; the electric rigs burn none. That is a real advantage and this simulation does not price it.

The race ends at the campsite, which is where the more consequential difference begins. Madison has no hookups of any kind. Both rigs arrive with a full trailer pack and both start drawing it down — air conditioning, refrigeration, thermal and control loads.

The gasoline rig can replenish where it sits, within the park's 8 a.m. to 8 p.m. generator window. The electric rig cannot. When its trailer pack runs down, the options are to drive 14 miles to West Yellowstone and sit on a Level 2 charger for several hours, or to leave.

For a two-night stay this is irrelevant. For a week it is the whole trip. That distinction is not visible in any door-to-door number, and for many owners it matters more than the four hours.

The infrastructure background to this simulation is on Charging Infrastructure. The measured transfer figures are on V2V AC Energy Transfer, and the trailer-side loads on Trailer Load & Thermal.