In theory, plug-in hybrid electric vehicles offer an alluring alternative to fully electric ones. They give drivers 20 to 65 miles of electric-only range for their daily use, plus a gasoline engine in reserve for longer trips or when they can’t recharge. The benefits of PHEVs come when drivers plug them in regularly—often overnight—to recharge their battery packs. Don’t plug it in and you get a gas-powered car that’s heavier and potentially has more emissions from lugging around a battery pack of which only a fraction gets used.
Therein lies the rub. In the 2020s, we simply don’t know whether the bulk of PHEVs sold in the U.S. are ever plugged in—and if so, how often and how much. Their makers won’t tell us.
And with PHEVs gaining momentum as the great potential “in-between step” for customers who aren’t ready to go fully electric, it’s worth asking: Will people actually use these cars as they were designed, or will they end up being a kind of wasted effort in the battle against emissions?
‘Why Would I Want A 30-Mile EV?’
Some say PHEVs are the “best of both worlds,” as Car and Driver anointed them in a comprehensive May explainer on the fast-growing technology. And plug-in hybrids have many advocates and fans, among them current and former owners of the 2011-2019 Chevrolet Volt, the best-known PHEV sold in the U.S.
Many journalists in and out of the automotive space have repeated recent automaker claims that these types of hybrids might bridge the gap between gas cars and electric ones, although they don’t often question how mainstream drivers will use them.
PHEVs might also be viewed as an auto engineer’s response to a regulator’s demand for some degree of zero-emission running that no car shopper has ever walked into a showroom and asked for. They’re a very rational solution to an average use case, but they’re virtually impossible for shoppers to understand without detailed education. No car shopper walks into a Chevy or Toyota dealer to ask for a slightly electric car with a gasoline backup.
Automaker marketing hasn’t helped much to explain them either. The closest slogan to date has been Honda’s, “It runs on electric, has gas if you need it,” from the 30-second ad it released for its 2018-2021 Honda Clarity Plug-In Hybrid.
But far more salespeople have to negotiate a conversation something like the following:
Shopper: So it’s a hybrid, right, like my niece’s Prius? I fill it up and get great gas mileage?
Salesperson: Yeah, but it also runs on electricity. Y’know, like a Tesla. For enough miles to do your daily driving.
Shopper: Oh! Cool, a guy at work has a Tesla, it’s really fast. So how far does it go?
Salesperson: Well, there’s 33 miles of electric range, and then …
Shopper: Wait, what? Huh? I thought it was electric. Why would I buy an EV that only goes 33 miles? Forget about this electric hybrid thing. I want to see a normal car.
Yeah, that may be an exaggeration. But it’s not as far from the truth as you might expect.
Show Us The Data
For various reasons, automakers have had an on-again, off-again relationship with PHEVs.
Generally, they don’t love building them, as they offer the higher costs of rechargeable battery EVs along with the mechanical complexities and repair issues of a standard gasoline powertrain on top.
They tend to come and go in the marketplace more than other types of vehicles; examples include the Chevy Volt, the now-discontinued BMW 330e, the Honda Accord for one model year only, the Polestar 1, the original Hyundai Ioniq, and a few others. The PHEV: Always a bridesmaid but never the bride.
Arguably Volvo has banked on PHEVs longer than most, offering a variety of sedans, wagons and SUVs with gas engines and plugs. But since 2021, Toyota and Jeep have periodically swapped bragging rights to the best-selling PHEV in the U.S. Toyota’s Prius Prime and RAV4 Prime sold 26,700 units last year (plus another 5,300 for the PHEV model of the Lexus NX), while Jeep’s two 4xe models (Wrangler, Grand Cherokee) plus its Pacifica Hybrid together managed a whopping 137,100 sales.
PHEV advocates, of whom there are many, simply presume as a matter of faith that the average buyer will have been educated on how to plug in and the benefits of doing so; and will, of course, actually plug in once they understand how swell that will be.
That would be nice, if true. Whether it is true turns out to be a very different question. We reached out to several automakers to ask what they think about this subject, and the lack of data speaks volumes.
TOYOTA: The king of hybrid cars refuses to give data on its PHEV buyers’ plugging-in behavior to reporters, including this one. Aaron Fowles of the carmaker’s mobility communications group sent Inside EVs the following statement:
While Toyota does have data on PHEV vehicles and charging behavior, we are declining the opportunity to respond at this time. Within Toyota, multiple teams collect and analyze data, and, when it comes to data collection and analysis, there is a wide range of variables related to things such as location, owner behavior, and other extenuating factors. As such, there is not consensus in the data or interpretation of the data to provide what we feel to be accurate responses, so we would like to respectfully hold off for now.
Well, yes, exactly: It’s precisely that owner behavior we asked you about.
It might be reasonable to suggest Toyota’s 2012-2016 Prius Prime Plug-In Hybrid, with a mere 11 miles of electric range, may not have been plugged in much. The year it launched, it was the sole Prius that retained the coveted California carpool-lane access sticker after the state ended that privilege for hybrids without plugs in June 2011.
So we asked Toyota for plugging-in data split among the four PHEVs it’s sold to date: that first Prius PHEV, the first-generation 2017-2022 Prius Prime (25 miles), the RAV4 Prime (42 miles) launched for 2021, and the current Prius Prime (40 or 45 miles) launched for 2023. The company would not provide it.
JEEP: In some ways, the PHEV narrative from the storied 4x4 brand is more perplexing. Last October, Jim Morrison, the head of Jeep North America from 2019 to 2023, told the Detroit Free Press that 90% of 4xe owners it surveyed charged their vehicles an average of five times a week. He didn’t comment on miles covered on grid electricity, or what percentage of total miles they represented. The data came, he said, from 50,000 4xe owners who opted into monitoring their charging and driving behavior.
That rate would represent by far the highest rate of plugging-in among any model of PHEV offered by any maker—higher even than the early-adopter Chevrolet Volt users. Yet the statistic is also somewhat puzzling, because a Stellantis employee who dug into related questions told us 18 months ago that versions 3 and 4 of the company’s UConnect telematics system did not collect data on charging behavior.
That would mean the 2016-2023 Pacifica (plug-in) Hybrids and the 2021-2023 Wrangler 4xe and 2022-2023 Grand Cherokee 4xe models, which used those systems, did not provide data on plugging in. We believe UConnect 5 now has that capability, but did those 50,000 owners all have the newer version that launched in the 2024 model year? In other words, it's not clear how we know this claim is true.
Moreover, when it launched in 2021, the Wrangler 4xe came with a lease deal that made the PHEV trim by far the best value among Wrangler models. That was a far easier selling point for salespeople than explaining how a plug worked and why. And it led to anecdotes like one from auto writer Adam Tonge, who noted his neighbors bought a 4xe purely for its low lease cost and because they liked the color—and had no idea it plugged in.
We asked Jeep for more details on the survey methodology, the electric miles covered, and which data could be collected by different UConnect versions. In particular, we wanted to know if the 90% figure represented ALL 4xe drivers or only a subset that volunteered to respond to a survey, a far less valid methodology than the aggregated data for all 4xes that we sought.
Despite many emails back and forth, Jeep would not provide any further responses or data. The company’s Dianna Gutierrez said it was “not able to disclose this information, as it’s proprietary information to the company.”
As for several other brands, here's what they said. (Note this is not an exhaustive list of all makers selling PHEVs in the U.S.):
HYUNDAI does not track plugging-in behavior, according to a spokesperson.
KIA told the Free Press last fall that of its three PHEV models, 70% of Niro owners plug in daily, 80% of Sorento owners, and 62% of Sportage owners. These results, however, come from a sample of 379 owners who self-reported their behavior, which survey experts will tell you is far from a statistically valid method. Spokesperson James Bell also told Automotive News in March that 87% of its PHEV drivers plug in daily or “multiple times per week.”
MITSUBISHI did not track plugging-in behavior in its 2018-2022 Outlander PHEV. While it could do so in the current generation, launched in 2023, it does not do so, according to spokesperson Jeremy Barnes.
VOLVO’s most recent data was from 2019 when its PHEVs covered 37 %of total miles in “Engine Off” mode—which blends miles covered on grid power with those in electric-only mode when operating as a conventional hybrid after the battery is depleted.
Volvo’s Thomas McIntyre Schultz suggested that since the company has boosted the battery size and electric range of its newest PHEV variants, that percentage may well be higher for the more recent models.
Early Adopters Were Eager To Plug In
It wasn’t always this way. The best-known PHEV may be the late, lamented Chevy Volt, which ran for two generations and nine model years from 2011 to 2019. Total U.S. sales were 157,000, never hitting 25,000 a year.
In the 2010s, GM and Ford proudly discussed the charging behavior of their Volt and Energi (Fusion and C-Max) plug-in hybrid buyers. First-generation Volt owners, with 35 to 39 miles of electric range, covered 63% of their miles on electricity. The second generation, with 53 miles of EPA-rated range, had rates as high as 80 percent. Ford said its Fusion and C-Max Energi plug-in hybrids, with 20 miles of range, covered half their miles on electricity (from grid power plus hybrid regeneration).
But the Volt and the Ford Energis a decade ago were for very, very early adopters—the buyers who knew what they were, and spent more time educating random salespeople about how they worked than asking questions about the car. Most people who bought a Volt understood it well before entering a showroom. And they plugged in at every available opportunity. That produced startling photos of extension cords strung from third-floor hotel windows and other unapproved kludges that let drivers recharge at every opportunity.
That was then; this is now.
Yet even back then, people knew about the problem of PHEVs that were never plugged in. A famous example surfaced in 2014: a fleet of 2011-2012 Chevy Volts whose data showed lifetime gas mileage of 34 to 39 mpg, matching the EPA ratings when running only on gasoline. They were fleet vehicles whose company drivers were likely reimbursed for gasoline expenses—but not for plugging in at home. So they didn’t plug them in, ever.
Meanwhile, many early-adopter Chevy Volt buyers have likely moved on, to the dozens of battery-electric vehicles now on sale in the U.S. (When the Volt went on sale in December 2010, the Tesla Model S wasn’t in production, and the sole mainstream EV you could buy was the Nissan Leaf. It was odd-looking and offered an underwhelming 74 miles of EPA-rated range, only twice the e-range of the Volt itself.)
More than a decade later, PHEVs remain a small piece of total U.S. sales. Last year, plug-in hybrids were just 2% of sales: 278,500 units out of 15.0 million vehicles sold. That contrasts to 1.1 million battery-electric vehicles sold (about half of them Teslas), or 8.0 percent—meaning four BEVs are sold for every PHEV.
Longer-Range PHEVs Cover More E-Miles
Part of the problem may be that most PHEVs sold in the U.S. over the past decade, the Volt aside, have offered quite low electric ranges (under 30 miles). It’s accepted wisdom that the more e-range a PHEV offers, the more it’s plugged in—and hence the more electric miles it covers. And that wisdom has been supported by a variety of studies.
A study for the California Air Resources Board, issued in April 2020 and titled Advanced Plug-in Electric Vehicle Travel and Charging Behavior Final Report, concluded:
Short-range PHEVs as a whole have utility factors significantly lower than expected, because of driving and charging behavior and a higher share of users who drive on gas only. Among households with one [electric vehicle] and one internal combustion engine vehicle (ICEV), those with a BEV have higher utility factors than those with a PHEV. When comparing greenhouse gas (GHG) emissions per household, the efficient gasoline engines of the PHEVs lead to reduced GHG emissions and environmental impact, but still BEV households present better results.
In other words, battery electric vehicles travel more electric miles than PHEVs do, which may be logical. But, crucially, those plug-in hybrids cover a lot fewer electric miles than regulators expected from calculations of their zero-emission miles in the rules they wrote.
Conclusions of that ilk—and the Volt data—led to the formation in July 2019 of what was called the Strong PHEV Coalition. Made up of “a broad group of electric transportation veterans,” the group lobbied CARB, which sets emissions rules for California that have been adopted by more than a dozen other U.S. states, from 2020 through 2023 to require plug-in hybrids to have ranges of at least 60 miles (less for larger vehicle categories) to get credit as zero-emission vehicles in the state from 2026 on.
It worked, more or less. Per the regulations issued in August 2022, “PHEVs must have an all-electric range of at least 50 miles under real-world driving conditions. In addition, automakers will be allowed to meet no more than 20% of their overall ZEV requirement with PHEVs.” In other words, 2025 is the last model year in which PHEVs sold in California with less than 50 miles of e-range can count toward the state’s emissions reductions.
Regulators Are Waking Up
Still, the question of whether U.S. PHEVs get plugged in is hardly a new one. A December 2022 paper from the International Council on Clean Transportation (ICCT), titled Real World Usage of Plug-In Hybrid Vehicles in the United States, summarized its findings as follows:
Real-world electric drive share may be 26%–56% lower and real-world fuel consumption may be 42%–67% higher than assumed within EPA’s labeling program for light-duty vehicles. We find that current PHEVs show electric drive shares much lower than assumed in EPA labeling. These new datasets present strong evidence that real-world electric drive share is far below the utility factor label rating. A consequence of this comparatively low electric drive share is that real-world fuel consumption is 42%–67% higher than EPA-label fuel consumption.
Emphasis ours. In other words, EPA assumptions about how much PHEVs run on electric power alone are wildly optimistic.
Then there’s the problem of how they’re actually driven. A March 2024 study by the European Union concluded plug-in hybrid electric vehicles studied in 2021 created far higher emissions than previously estimated—an average of 3.5 times as much as tests done in laboratory conditions suggest.
Unlike the Volt, most of those PHEVs didn’t stay in electric mode all the time, but often switched on their engines to supply power when the electric motor couldn’t. The study said they “are charged and driven in electric mode much less than how they were expected to be used.” Driving to keep up with traffic burned far more gasoline than did the lab tests.
(As for China, which also has a huge PHEV market in addition to a BEV one under its "New Energy Vehicle" push, data there is difficult to parse. That 2021 ICCT study indicated China had "low charging frequency, whereas PHEVs in Norway and the United States appear to be charged more often than in Germany or China.")
All these factors have led regulators to think harder about what kinds of PHEVs should be incentivized—and how to ensure they actually operate in zero-emission mode. As a result, CARB suggested to the EPA that it “require auto manufacturers to collect and report in-use operational data at discrete intervals on PHEVs in future model years … to more accurately assess the greenhouse gas emissions associated with different PHEVs.”
That didn’t happen. The final version of the CAFÉ standards for model years 2027 and beyond wholly ignores the issue of whether PHEVs are plugged in at all—while granting more generous allowances to automakers for each PHEV they sell. As NHTSA notes (on page 63 of a 104-page document), it is required to use the EPA’s test procedures and that agency’s “utility factor” in calculating fuel-economy compliance. That factor is widely viewed as overly optimistic, i.e. it assumes PHEVs cover more miles on electricity alone than they do in the real world.
The New Compliance Cars?
In the end, unless and until automakers in the U.S. provide data showing their plug-in hybrids are actually plugged in for a notable proportion of their road miles, PHEVs are no more than an easy out for automakers to meet stricter fuel economy and emissions rules on paper. If they already sell hybrids, they can add a bigger battery and a plug to existing models, and then toss them over the fence to their dealers.
Because, remember, OEMs get the emission credits for selling the PHEV. How it’s used is simply Not Their Problem. So they have zero reason to care if they're ever plugged in. Which means, absent data to show they’re plugged in, PHEVs are compliance cars until proven otherwise.
What’s a compliance car, you ask? Twelve years ago, California imposed zero-emission vehicle requirements on the six highest-selling automakers in the state: GM, Ford, FiatChrysler, Toyota, Honda, and Nissan. GM had the Chevy Volt; Nissan had the Leaf.
But without any EV programs, the other four had to offer zero-emission vehicles and sell them in high enough numbers to keep them on the right side of the rules. The Fiat 500e, Ford Focus Electric, Honda Fit EV, and Toyota RAV4 EV (with a Tesla battery and drivetrain) were “compliance cars”—sold in exactly the right volume, only in states with those regulations (e.g. California), to stay compliant with the state’s emission rules.
Automakers didn’t want to sell them, didn’t like them, and often talked them down. The product manager at Ford’s Focus Electric launch event spent more time on reasons people wouldn’t buy the car than why it might be a good solution for some. The late Sergio Marchionne, then CEO of Fiat Chrysler, famously begged people not to buy the Fiat 500e because, he said, his company lost $14,000 on each one. (It nonetheless had to sell roughly 25,000 to stay compliant.)
It’s increasingly plausible PHEVs will be only compliance cars, for at least Toyota and Stellantis. While Toyota now sells the mediocre bZ4X and Lexus RZ, its Prime PHEV models outsell them in the U.S. Stellantis has PHEVs from Alfa Romeo, Chrysler, Dodge, and Jeep, and is by far the leading PHEV seller here. It also paid $190.7 million in fines for failing to meet fuel-economy rules.
Higher PHEV sales offer more emissions elbow room—even if they’re never plugged in.
A Bridge To Where?
These days, any reason for PHEVs to exist should depend on owners Plugging. The. Damn. Things. In.
Their mere existence is being subsidized by tax dollars, but it’s unclear if they’re doing anything to reduce emissions of climate-warming carbon dioxide–which was the goal the subsidies are meant to incentivize.
Right now, seven of them qualify for federal purchase incentives—including both Jeep 4xe models and the Chrysler Pacifica Plug-In Hybrid. Neither Toyota Prime model makes the grade. Several dozen other PHEVs no longer receive subsidies when purchased, though every single one can qualify if it’s leased. (That gigantic loophole is a story for another day.)
Subsidies and state incentives given to PHEVs that aren’t plugged in only continue to encourage using fossil fuels over grid electricity for transport. And that would be antithetical to the goal of those subsidies. (Badly designed incentives are yet another separate discussion. Waiter, a double, please.)
So are they plugged in? The OEMs are the only people who know. And they aren’t talking. That seems very suspicious—and leads to some very unhappy conclusions.
John Voelcker covers advanced auto technologies and energy policy as a reporter and analyst, specializing in electric vehicles and the energy ecosystem around them. He edited Green Car Reports for nine years, and his work has appeared in Car and Driver, The Drive, Forbes Wheels, Wired, Popular Science and NPR's "All Things Considered."
Top graphic credit Sam Woolley.
