Thor’s Hybrid-Electric RV Is a House on Wheels That Drives Like a Car

No one buys an RV for the driving experience. You own a house on wheels so you can visit the world’s wildest places and sleep in civilized bliss. So you can spatchcock a chicken while camping. So you can take a washing machine with you on vacation.

RV travel is about the destination, not the journey of steering a 35-foot box through traffic, which explains why the chassis and powertrains underpinning today’s RVs have hardly changed in the past 40 years even as cars have become computerized and electrified marvels. “Modern” motorhomes are noisy, clumsy machines with the body control of a one-year-old who missed his nap and acceleration that feels like it could be measured in minutes, not seconds.

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That’s about to change with arrival of the first plug-in hybrid motorhome. Next year, RV manufacturer Thor Industries and commercial EV startup Harbinger plan to launch a production Class A motorhome driven by an electric motor drawing power from nearly one ton of lithium-ion batteries and a gas-burning four-cylinder spinning a generator. That powertrain is packaged in a medium-duty chassis that Harbinger designed from a clean sheet, which gave engineers the opportunity to rethink the steering, suspension, and brakes, too. Having driven the prototype pictured here, it’s hard to overstate the transformative effect of all this. Harbinger and Thor have created an RV that’s almost carlike in how it drives.

Big Battery, Big Torque, Tiny Engine

The revolution starts, as it so often does these days, with an electric motor. Designed and built by Harbinger, the single permanent-magnet motor turns the rear wheels through a single-speed transmission with up to 1,140 lb-ft of torque and 440 horsepower. Electricity is stored in nickel-cobalt-aluminum-oxide 2170 lithium-ion battery cells—the same size, shape, and chemistry as those in the long-range Tesla Model 3—bundled by Harbinger into 800-volt, 35-kWh battery packs. In the Thor Class A prototype, four of those packs have been wired in parallel, creating an 1,848-pound battery with a total capacity of 140 kWh, just slightly more than the Rivian R1T holds in its Large pack.

Harbinger isn’t saying who makes the small naturally aspirated inline four-cylinder (if you can ID it from the photo here, find your way to my email inbox). Fed by a 40-gallon gas tank, the engine is decoupled from the wheels and only contributes power in the form of electricity. Even though it runs at a constant 4,500 rpm, the four-cylinder should make for a quiet ride. In most Class A gas RVs, a Ford 7.3-liter V-8 sits directly below the driver’s right ear. Harbinger’s chassis packages the engine behind the rear axle, some 15 feet behind the driver.

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Complicating Matters

What seems like a straightforward series plug-in hybrid powertrain gets complicated when you understand how all the pieces work together. Unlike most plug-in hybrid cars and SUVs, this one won’t wait until the battery is depleted to fire the combustion engine. That’s because the gas generator makes just 67 horsepower, and it takes more than that to push the blunt front end of an RV through the atmosphere at anything faster than 50 mph. For Thor’s RV to maintain highway speeds, the electric motor needs to draw at least some of its power from the battery.

In other words, once the battery goes flat, the RV is limited to 50 mph—and that’s on level ground. Thor estimates its RV will have a range of 500 miles, at which point you can either plug it in, park it to let the gas engine charge the battery, or continue driving with a sub-50-mph top speed.

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Harbinger says the battery will charge from 20 to 90 percent in one hour, but Thor execs don’t expect many customers will bother with fast-charging stations—most of which aren’t designed to accommodate a 30-foot RV. More likely, owners will leave home with a full battery, make it to the campground on that charge, and plug into a 30- or 50-amp power pole at their site. Recharging a nearly dead battery in these situations will take anywhere from 15 to 24 hours.

Thor and Harbinger started their collaboration with the goal of developing a pure EV motorhome with 250 miles of range, but both parties quickly realized that product wouldn’t work for most customers. The plug-in hybrid they built instead aims to meet an RVer’s needs at a price competitive with a gas motorhome. A bigger generator could extend the PHEV’s range from 500 to 800 miles, but Harbinger CEO John Harris says that would add cost for capability that few buyers would actually use.

All of this is a long way of saying that the powertrain strategy will involve running the engine early and often to make the battery last as long as possible. Harbinger is still fine-tuning the calibration, but it’s likely that if the RV is moving, the engine will be burning gas.

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Domesticating the American Interstate Buffalo

So put an asterisk on the driving impressions you’re about to read, because the gas engine was disabled during my demonstration drive. I can’t tell you if this gas-electric hybrid is any quieter or more civilized than today’s RVs. I can tell you that, with the battery delivering full juice to the electric motor, this RV moves with the easy authority of a modern SUV.

Anyone who’s made the transition from a gas to an electric car knows how a big jolt of immediate torque changes driving. In an RV, the baseline is so much lower—the current products are so basic—that smooth and effortless electric acceleration feels even more revolutionary. The electric motor makes the 7.3-liter Ford V-8 known as Godzilla feel as menacing as a gecko. I’m pretty sure the 14,500-pound Thor/Harbinger prototype can outrun some brand-new economy cars.

It's a lot of speed for a 28.5-foot RV, especially in a parking lot barricaded to be smaller than an autocross course. Keeping the RV corralled, though, highlights Harbinger’s chassis work. A brake-by-wire system reins in speed confidently and with immediate bite—possibly too much initial bite, but that’s the advantage of electronic chassis controls: They can be reprogrammed in minutes. Brake-by-wire also makes it easy for the engineers to blend the friction brakes and regenerative braking. Using the motor to slow the RV on downhill grades simultaneously boosts the vehicle’s range and keeps the driver from boiling the brake fluid.

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Harbinger has replaced the conventional leaf-sprung solid front axle with massive forged control arms and coil springs that improve ride and handling and allow for more sophisticated suspension kinematics. Chief among the benefits: The front wheels can turn up to 55 degrees (50 degrees is common in the industry), enabling a tighter turning circle for easier campground maneuvering.

A De Dion suspension at the rear axle replaces the usual live axle and, along with the front suspension, saves hundreds of pounds. Harbinger claims its whole medium-duty chassis—battery packs and all—weighs more than today’s gas alternatives but less than diesel versions.

The low center of gravity reduces roll, and electrically assisted power steering delivers on-center fidelity where current RVs are loose and vague. The glacially slow steering rack (5.3 turns lock to lock) still requires hand-over-hand-over-hand movements to reach full lock, but Harbinger’s Harris says the ratio will get quicker before production. Further down the line, the company plans to remove the intermediate shaft altogether, turning the same hardware into a true steer-by-wire system much like the Tesla Cybertruck’s. An infinitely variable ratio would make it possible to park an RV without ever taking your hands off the wheel. Steer-by-wire would also give manufacturers like Thor complete freedom over where the driver sits.

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Modernizing the chassis also means there’s a full suite of bacon-savers onboard, including antilock brakes, traction control, and stability control. Eventually Harbinger plans to offer the same driver assistance features that have become common on cars and SUVs, including automated emergency braking, adaptive cruise control, and lane centering assist.

Benefits Beyond the Driver’s Seat

There are big benefits beyond improving the driving experience, too. Harbinger ballparks the fuel economy improvement at 50 percent over a gas vehicle, although even a 50 percent improvement on “atrocious” is still not great. The provided range and fuel capacity suggests a 12.5-mpg average, and that doesn’t account for the electricity drained from the battery.

The gas-electric powertrain also opens the door to rethink things on the house-building side of the business. The 140-kWh traction battery serves double duty as the house battery that powers the fridge, the lights, the TV, and the microwave, which should make boondocking (camping without a power hookup) a breeze. The gas engine eliminates the need for a dedicated house generator, and the battery capacity is big enough that Thor could choose to eliminate the propane system and just use electric appliances. The heat pump that manages the battery and motor temperatures also cools the cabin, and it’s powerful enough Thor can downsize the house air conditioner and move it from the roof to under the vehicle. That improves the aerodynamics and leaves a huge, open platform for solar panels. Parked at home, the RV’s massive battery could serve as a backup power source during an outage, providing electricity for days.

Moving Fast and Hopefully Not Breaking Things

McKay Featherstone, senior vice president of global innovation at Thor Industries, boasts that the RV industry develops products in months, not years like the auto industry. Those developments have traditionally revolved around making beds fold out of new and exciting places, but the company is keeping its foot on the gas—er, accelerator—even with a paradigm shift in powertrain technology. It took 16 years from the debut of the Chevrolet Volt for someone to cook up a viable plug-in hybrid RV. With Thor embracing Harbinger’s platform, it’s moving into the bring-it-to-market-in-months part of the development cycle.

There’s still a lot of work ahead to turn the Thor prototype into a production vehicle, and yet the company is promising at least one of its brands—Tiffin, Entegra Coach, Jayco, or Thor Motor Coach—will have a Class A RV based on Harbinger’s hybrid platform for sale late next year. If Harbinger can deliver a reliable chassis and powertrain right out of the gate when it starts production later this year, expect Thor’s plug-in hybrid to mark the start of the RV’s electrification era.