The Bridge? What Are EREVs, and Why Are They Being Hailed as a Breakthrough Powertrain?
As it turns out, EV and ICE might go together like chocolate and peanut butter.
While there's been no shortage of anti-EV fearmongering over the past few years, rife with claims that mandates and quotas are forcing buyers into battery-powered cars before they're ready, the truth is that our transition to an electrified future will be a little less dramatic and a lot more gradual.
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Take for example a series-parallel hybrid like the Toyota Prius, which has been around for decades now, and more recently vehicles equipped with a plug-in hybrid powertrain, one that offers some amount of emissions-free range thanks to the use of a bigger battery.
Now there's another step on the journey to full electrification that's lately been gaining some momentum in the automotive space. They're called extended-range EVs, or EREVs, and they serve to split the difference between a plug-in hybrid and a full-on battery-powered machine, offering many of the benefits of both. What are EREVs, and are they worth considering? Let's dig into the details.
What Is an EREV?
The technology behind an extended-range EV is nothing new. In fact, the basic concept has been used in freight trains for over 100 years now. It's quite common in marine applications, as well. In those worlds they're often called diesel-electrics, but the same concepts apply here.
In an automotive application, the simplest way to think about an EREV is to imagine a typical EV. One or more electric motors turn the wheels to move the vehicle, all powered by a large battery pack.
So much so familiar. What's different about an EREV, also commonly called a series hybrid, is that there's an internal combustion engine somewhere inside the car, much like a plug-in hybrid. The difference here, though, is that the engine is in no way connected to the drivetrain. It cannot directly move the car. It only acts as an onboard generator to recharge the battery.
With this kind of car, you can plug it in to charge it and drive it emissions-free like a typical EV. However, when you want to go farther than that battery can manage, the gas engine can spin up and start recharging the battery on the go, in theory giving the kind of quick-refueling and indefinite range of a gasoline-powered car.
What Are an EREV's Advantages Over a Plug-In Hybrid?
Both EREVs and traditional plug-in hybrids can be charged directly and allow some amount of emissions-free driving. However, EREVs have larger batteries and so offer much more range before relying on the gasoline engine. So if you primarily want an EV but want the ability to road-trip worry-free, they're a good solution.
EREVs also have the potential to be more efficient than plug-in hybrids. Because that engine only charges the battery, it can be optimized for running in a narrow rpm range. It doesn't need to provide good throttle response or drivability, and parasitic losses from the transmission are minimized. The net result? You get more energy out of a given gallon of gasoline, which is better for both the environment and your wallet.
This setup also removes a lot of mechanical complexity from the equation. Traditional automotive hybrid systems often rely on complex transmissions with planetary gears to manage the hand-off of power between the motor(s) and engine. In an EREV, the power driving the car only ever comes from the electric motors.
What Are an EREV's Advantages Over an EV?
Again, an EREV is basically an EV, but an EV with an onboard generator. The obvious advantage here is range. For example, Scout promises that its upcoming Traveler SUV will offer up to 350 miles of range in EV form. However, go with the EREV version (which Scout calls a Harvester), and you can have up to 500 miles of range.
And you'll have full functionality. "Full usage parameters, 100 percent," Scout CEO Scott Keogh told us at this year's CES. "Zero to 60 times will be a little bit slower, but you're going to be able to tow. You'll have 100 percent gradeability."
Towing might just be an EREV's killer app. "When you're towing a big, heavy trailer, typically your efficiency drops by about half, even with gas vehicles," Sam Abuelsamid, VP of market research at Telemetry Insights, said.
Losing half your efficiency with a gasoline-powered vehicle gets expensive, but you can at least quickly refuel your tow rig and get back on the move when you run out of fuel. With an electric truck, things can be a lot more complicated.
"If you get to a charging station and it just has back-in bays, you'll probably have to disconnect your trailer, pull in, charge, sit there for 45 minutes to an hour or more for these bigger vehicles, then hook up your vehicle again and be on your way," Abuelsamid said. "It's not convenient."
With an EREV, you could just gas up like normal. And then there's also the advantage of simply being able to travel out into the wilds on a moment's notice, areas where the charging infrastructure simply might not exist.
That makes EREVs particularly desirable for anyone who loves impromptu journeys out into the charger-free wilds, especially those who might be taking an Airstream along for the journey.
What Disadvantages Do EREVs Have?
One potential disadvantage of an EREV is cost. Adding an internal combustion engine into the mix, plus a fuel tank and associated plumbing, will drive up the cost of the vehicle along with its weight—assuming the battery pack stays the same size.
However, one way to cut down on that cost would be to reduce the battery pack size, creating a vehicle that could still travel a good range emissions-free but would save weight and cost over a fully electric model.
EREVs will also require more maintenance than a typical EV. By keeping internal combustion in the mix, you're keeping around such fun things as oil changes and spark plug replacements, jobs you simply don't have to worry about in an EV.
However, since EREV engines are relatively small-displacement and don't see anywhere near the stresses you might in a traditional car, those service intervals should be fewer and farther between.
"It should require less maintenance than what you have for a typical internal combustion truck,” Abuelsamid said, “in part because you're probably going to be using that engine a lot less.” You might be looking at an oil change once a year, plus the usual checks for brake and tire wear, but that should be about it.
One final disadvantage is noise. While it's easy to love the acoustic energy of a free-revving engine, the sound of an effective generator droning along at a constant rpm in an EREV is unlikely to be an evocative one.
What EREVs Are on the Market Today?
Currently, there are no new EREVs available for sale, at least not here in America, although that's set to change soon. In China, however, EREVs are all the rage, which we found out last year during our MotorTrend trip to China, where we evaluated EREVs including the 1,180-hp Yangwang U8.
As mentioned above, Scout Motors plans to offer a so-called Harvester package for its Traveler SUV and Terra truck. This will include a small-displacement internal combustion engine that will effectively slot into the ladder-frame chassis, sitting at the rear of the vehicle.
This positioning ensures there will be no loss in cargo space or functionality in the vehicle, and since both of these vehicles are quite long (190.9 inches in the case of the Traveler, 229.2 for the Terra), keeping the generator at the rear should keep noise in the cabin to a minimum. Scout's EREVs are expected to hit the market in 2027.
Ram is also leaning into the EREV approach to boost the range and capability of its upcoming Ram 1500 Ramcharger. There, the combustion side will be handled by a 3.6-liter V-6 that won't be connected to the wheels in any way. It will only be responsible for spinning a generator to fill up the battery while the truck is in motion.
Two electric motors will provide 663 hp and 615 lb-ft of torque, powered by a 92-kWh battery with an estimated range of around 150 miles. That doesn't sound great on its own, but factor in the boost provided by that Pentastar V-6 and its 27-gallon fuel tank, and you're looking at 690 miles of maximum range.
Options like this might just become must-have accessories for anyone needing an electric truck for daily duties but wanting to pull a fifth wheel hundreds of miles for weekend getaways. No surprise that Ford, too, is looking to get in on the EREV game in its next-generation larger trucks and SUVs.
Ford's vehicles are likely some time away, as are Scout's Harvester-equipped truck and SUV, which won't be out until 2027. The Ramcharger is coming much sooner, due sometime this year, but those looking to buy a new EREV today are unfortunately out of luck.
That is, unless they're willing to go with something pre-owned. In that case, you have options.
Well, option, anyway. BMW offered an onboard generator for its i3 compact EV. BMW called it REx, short for "range extender," and it included a tiny, 0.6-liter engine borrowed from a BMW Motorrad scooter. It was only really intended to be something of a last resort, as the car would almost completely deplete the battery before firing up the engine, meaning its performance was quite limited with the engine on. This wasn't a particularly popular option, so i3s with the REx option are rare, but they are out there.
Your other option is even rarer, the Fisker Karma. Henrik Fisker's first flop was a lovely sedan that never found much love in the market.
Finally, we'll give the Chevrolet Volt an honorable mention here. Though positioned as a series hybrid, the Volt could use its engine to directly power the wheels at highway speeds. In that way, it's not a true EREV, but given that Chevrolet sold hundreds of thousands of the things globally, they're certainly much easier to find than those other options and generally regarded to be great cars.
Are EREVs the Future?
As we've seen, EREVs offer some significant advantages over both a full EV and a plug-in hybrid. However, they aren't without their trade-offs. Are they the way forward, or just another stopgap measure for those still unwilling to commit to an electrified future?
"An EREV gets you the best of both worlds," Abuelsamid said, particularly for current, heavy-duty applications, where the cost of a small engine and fuel tank is significantly less than the giant battery that would otherwise be required to provide decent range and towing capability.
"Long-term, those larger vehicles, I think, will stay with an EREV," he said, at least as an option.
As EV technologies improve and our charging infrastructure expands, onboard generators may become less attractive. At that point we may truly conquer range anxiety, even for those pulling a horse trailer most days.
But until then, it's great to know that the industry has a solution that'll keep us moving in the right direction.
