Compared to gasoline cars, conventional hybrids, or battery-electric vehicles, understanding a plug-in hybrid can be particularly challenging. It operates akin to a regular hybrid, such as a Toyota Prius, yet presents an additional facet: functioning as an electric vehicle that recharges by plugging into a power source to energize a battery pack, enabling it to operate on electric power intermittently—but typically within a range of 20 to 60 miles.
This complexity often bewilders prospective car buyers. One commentator humorously suggested that plug-in hybrids are a solution devised by engineers to answer a question posed by bureaucrats, a question that no actual car buyer has ever raised: “How can I predominantly cover my anticipated daily mileage using electricity, while averting the range anxiety associated with a purely electric vehicle?”
The concept revolves around providing drivers who can charge their vehicles at home overnight with an electric range of 20 to 50 miles, adequate for their daily commuting and errands. According to data from the U.S. Department of Transportation, the average driver covers approximately 37 miles per day. However, for unforeseen longer trips or situations where charging isn’t feasible, these vehicles still function as fuel-efficient hybrids. For owners who primarily undertake short trips, the combustion engine might remain dormant for weeks, necessitating gasoline refills only every few months, provided they regularly recharge the vehicle.
Power-Split vs. Series Hybrids
There exist primarily two categories of plug-in hybrids: those that harmonize power derived from both the battery pack and the gasoline engine (referred to as “power-split hybrids”) and the far less common type where the gasoline engine functions solely as a generator to recharge the battery but lacks the ability to mechanically propel the wheels (known as “series hybrids”). The BMW i3 stands as a notable example of the latter.
The majority of power-split hybrids integrate torque from both the engine and the motor to propel the same axle. This configuration is employed by manufacturers like Toyota, Ford, and others. While many of these hybrids are front-wheel-drive vehicles, such as the Toyota Prius, some also offer all-wheel drive. All-wheel drive can be achieved through driveshafts that mechanically power the rear wheels (as seen in the 2005–2012 Ford Escape Hybrid) or via an electric motor that propels the rear wheels (as evident in the current Toyota Prius or RAV4 Hybrid).
Alternatively, a select few hybrids utilize the gasoline engine primarily to power one axle but incorporate an electric motor to drive the other end of the vehicle. The hybrid function occurs when the powertrain control system determines whether gasoline or electric power needs to supplement the mode already propelling the vehicle. This variant is known as a “through-the-road hybrid” because the engine and motor power combine exclusively through the four wheels, without interaction within the powertrain itself. While there are no vehicles solely powered by a gasoline engine for one axle and exclusively electric power for the other, a closely related example is the new Dodge Hornet R/T (and its similar counterpart, the Alfa Romeo Tonale). These models feature a robust electric motor propelling the rear wheels (thus functioning as rear-wheel drive in electric mode) while also integrating a small electric motor that assists the gas engine upfront.
Single Motor vs. Dual Motor Configurations in Plug-In Hybrids
However, drivers will discern a distinct variance in driving experience between plug-in hybrids equipped with a two-motor system, which collaborates through a planetary gearset to serve as a transmission (as seen in the Toyota and Ford models), and those employing a single electric motor positioned between the engine and a traditional automatic transmission (adopted in some newer Fords, all Hyundai and Kia models, Mazda, etc.).
The utilization of two motors and a planetary gearset allows for continuous adjustment of ratios. In contrast, an electric motor situated between an engine and gearbox propels the vehicle through that gearbox, resulting in the retention of standard shifting patterns even when operating in the electric mode. However, these shifts often tend to be less seamless compared to those from a conventional internal combustion engine powertrain.
Electric Power versus Total Power
Drivers will also observe a significant difference in the power output of Plug-in Hybrid Electric Vehicles (PHEVs) when operating solely on electricity in comparison to when they utilize gasoline alone or a combination of gasoline and electric power. For instance, consider the 2024 Mazda CX-90 PHEV: its electric motor is rated at 173 horsepower, yet the combined gasoline-electric hybrid system generates an overall output of 323 horsepower. Consequently, acceleration from 0 to 60 mph significantly decreases from a rapid 5.9 seconds when functioning as a hybrid to over 11 seconds in EV mode. This disparity in acceleration makes it challenging to keep pace with traffic or swiftly merge onto an interstate without engaging the gas engine.
The two iterations of the Chevrolet Volt (2011–2015 and 2016–2018) were distinctive among plug-in hybrids for delivering nearly identical performance, whether the car operated solely on battery power or in gasoline hybrid mode.
Plug-In Behavior: A Regulatory Challenge
The ultimate quandary concerning plug-in hybrids—pertaining not to the owners but to regulatory bodies—is whether these vehicles are actually connected to a power source. If they remain unconnected, they essentially function as marginally improved hybrids, adding weight, inflating costs, and frequently benefiting from substantial purchase incentives, even if they never utilize the electric grid.
Throughout the 2010s, the two leading plug-in hybrid manufacturers (GM and Ford) disclosed compiled data on owners’ practices of plugging in their vehicles to both the media and regulatory authorities. For instance, a 2013 report by the U.S. Department of Energy indicated that 75 percent of the miles covered by the Chevy Volt were powered by grid electricity.
Unfortunately, in the early 2020s, neither of the two primary plug-in hybrid manufacturers (Toyota and Jeep) were inclined to share data concerning the frequency or occurrence of their vehicles being connected to a power source. To them, it appears inconsequential. They receive regulatory acknowledgment for selling the vehicles, regardless of the owners’ usage patterns. Moreover, plug-in hybrids often come with incentives that salespeople can employ to lower the purchase price, making it comparable to that of a standard hybrid, even though the plug-in hybrid frequently boasts superior trim specifications, justifying its higher retail price.
