The Mammoth Overland WLY — pronounced “Wooly” — is a purpose-built cold-weather off-road teardrop trailer priced at $59,500. Using the HV as its base platform, the WLY adds an R25 insulated floor, wool-lined R12 walls, a Truma VarioHeat furnace, winterproofed heated water lines, and an 800Ah self-heating lithium battery bank. That same insulation works in reverse, which combined with the standard Dometic RTX 2000 air conditioner makes the WLY a genuine four-season trailer rather than a winter-only rig.
The Short Answer
The deciding question isn’t “do I camp in extreme cold.” It’s “do I want one trailer that performs at both temperature extremes.”
The WLY’s insulation package — R25 in the floor, R12 in the walls via wool lining — works in both directions. It holds heat in during winter and keeps heat out during summer, aided by a standard Dometic RTX 2000 air conditioner rated for ambient temperatures from 41°F to 126°F. Mammoth’s own framing for the trailer is “snow and surf,” and that’s an accurate description of the design intent.
Full Specifications
| Spec | Detail |
|---|---|
| Price | $59,500 |
| Base platform | HV teardrop |
| Floor insulation | R25 |
| Wall insulation | R12 (wool lined) |
| Heater | Truma VarioHeat, 11,500 BTU/hr |
| Air conditioning | Dometic RTX 2000 (41°F–126°F ambient) |
| Battery | 800Ah lithium (dual 400Ah self-heating) |
| Solar | Two 100W panels standard (200W total) |
| Generator | Included standard |
| Suspension | Timbren 3500HD independent |
| Tires | 33″ Toyo Open Country AT3 on 17″ bronze torque wheels |
| Water tank | 21 gallons |
| Water lines | Winterproofed, heated |
| Interior cabin height | 4′ 2″ |
The Wool Is Not a Gimmick
The WLY’s wall insulation comes from wool lining installed inside the cabin, and Mammoth is direct about the dual purpose: it raises the wall R-value to R12, and it replaces cold aluminum with a warm fabric surface.
That second point matters more than spec sheets capture. In a small, well-insulated cabin, the thing that actually makes you cold at 3 a.m. is brushing against a bare metal wall. Wool solves a comfort problem that insulation numbers alone don’t describe. It’s also an excellent insulator even when damp, naturally hypoallergenic, and fire-resistant.
Buyers choose from several standard wool colors — acorn, midnight blue, medium gray, and others — with plaid patterns available for $200, including Red and Black Buffalo, Denim Blue/Black check, and Blue and Olive Plaid.
The Heater: Why Mammoth Switched
The HV and ELE both use a Dickenson marine heater, an enclosed-fireplace design that Mammoth’s team openly says they love for its feel and efficiency. For the WLY, they switched to the Truma VarioHeat, and the reasoning is specific to cold-weather use.
The Truma VarioHeat is a propane-powered forced-air system rated at 11,500 BTU/hr — roughly the output required to heat a 600-square-foot house. The WLY’s cabin is nowhere near 600 square feet. Applied to a monocoque insulated shell that size, the result is fast, quiet temperature control with selectable airflow speeds, so it can correct a temperature swing rapidly and then run quietly overnight. A control module by the door handles temperature and airflow.
The practical version: set it before you leave for the day, come back to a warm trailer.
Water That Doesn’t Freeze
Cold-weather trailers routinely force owners to winterize and abandon their water systems below freezing. The WLY’s on-demand hot water system is winterproofed with heated lines, so the 21-gallon tank and plumbing stay usable in conditions that would sideline a standard trailer.
Power for Winter Conditions
Winter is the hardest season for trailer power: shorter days cut solar output, and standard lithium batteries can’t safely charge below freezing at all.
The WLY answers both. Its 800Ah bank consists of dual 400Ah self-heating lithium batteries, which can accept a charge in cold temperatures. Two 100W solar panels come standard, upgradeable to two 200W panels for $650. A generator is included standard rather than optional.
Snow and Surf
The Dometic RTX 2000 air conditioner carries over from the ELE. It’s rated for ambient temperatures from 41°F to 126°F, runs up to 12 hours, and draws only 19A in Eco mode — meaning it doesn’t destroy the battery bank to run it.
Combined with the R25 floor and R12 wool-lined walls, the same envelope that traps heat in winter keeps it out in summer. That’s the argument for the WLY over a dedicated winter trailer: it doesn’t sit idle for half the year.
Winter Gear Storage
The WLY includes MOLLE panel designs specifically intended for winter equipment — skis, snowshoes, snowboards — along with four exterior MOLLE panels, an extra-large modular observation platform, traction boards, two RotopaX, a Krazy Beaver shovel, LED yellow flood lights, amber roof rack lights, and an annex enclosure for changing out of snow gear before entering the cabin.
Frequently Asked Questions
How much does the Mammoth WLY cost? $59,500, with limited options: increased solar at $650, plaid wool at $200, and an upgraded shower enclosure at $535.
How is the WLY different from the HV? The WLY uses the HV as its base and adds R25 floor insulation, wool-lined R12 walls, a Truma VarioHeat furnace, winterproofed heated water lines, an 800Ah self-heating lithium battery bank, 33″ Toyo tires on bronze wheels, a Dometic RTX 2000 air conditioner, a generator, and winter-specific gear mounting. Many features that are options on the HV are standard on the WLY.
Does the WLY work in summer? Yes. The insulation works in both directions, and the standard Dometic RTX 2000 air conditioner is rated for ambient temperatures up to 126°F. Mammoth positions it as a “snow and surf” trailer.
Why wool insulation? Wool raises the wall R-value to R12, insulates well even when damp, is naturally hypoallergenic and fire-resistant, and replaces cold bare aluminum with a warm fabric surface inside the cabin.
Can the WLY’s batteries charge in freezing temperatures? Yes. The 800Ah bank uses dual 400Ah self-heating lithium batteries specifically so they can accept a charge in cold conditions, which standard lithium batteries cannot.
Ready to build your own WLY? Explore the full feature list or place your reservation directly with Mammoth Overland.