Barra’s blunt truth about plug-in hybrids exposes the policy math behind their “clean” label

A plug-in hybrid may appear to be an appearance of victory in the case of emissions on paper and an appearance of a regular car in everyday reality, and still, with no warn lights. It is that disconnect which was summed up by General Motors chief executive Mary Barra via a single sentence at an industry event: “Most people do not plug them in.”

The commentary is important in that the plug-in hybrid electric vehicles (PHEVs) have been promoted and regulated as an intermediate to driving on gasoline and complete battery-electric driving. Their performance is reliant on a basic routine-charging-but charging is optional as it is not the case with a battery-electric car. When the cable is kept in the coiled form, a large battery and an electric drive system are installed in the car, but it is based on the internal combustion engine.

Barra has told the company it is committed to fully electric vehicles as its “endgame,” but it is still considering what hybrids and PHEVs will be to its lineup. The engineering difference in such assessment is not hard. A traditional hybrid (HEV) does not require plugging in and exploits generative braking and power-split control. A PHEV is fitted with a larger battery that is supposed to be charged at the grid, regenerative braking aids, but it is not able to power the battery alone. Unless the battery is refilled off the vehicle, the benefits of the PHEV reduce, and the mass penalty remains. Consumer Reports has pointed out situations where such a tradeoff manifests itself as a decrease in the mileage after the electric range is reached.

It has long been known by regulators that the behavior of drivers can be the determining factor in the success or failure of PHEV climate value, but on-road data is narrowing the gap on this issue.

The international council on clean transport has examined self-reported and inspection based data and discovered that real-world electric driving may be 26%–56% lower than the supposed driving in the EPA labeling program, and that the actual fuel consumption can be much greater. The idea behind the study is not that PHEVs cannot operate in a clean manner, but that emissions performance is extremely sensitive to the frequency of charging–and mainstream drivers can not be expected to operate like early adopters that have reliable home or workplace charging.

The monitoring efforts of Europe are directed in the same direction but with another mechanism called mandatory on-board fuel consumption monitoring (OBFCM) devices that are mounted on new vehicles. Early Commission analysis of OBFCM submissions concluded that, for plug-in hybrids, real-world CO2 emissions were on average 3.5 times higher than laboratory type-approval values. That has been a much greater difference than the normal real-world difference that is observed with conventional petrol and diesel vehicles and further supports the thesis that the official ratings of PHEVs are usually a test of ability, rather than of common usage.

The policy reaction has been more concerned with the “utility factors” the modeled portion of driving that is electrically done that is utilized to scale the outcomes of test-cycle to a regulatory CO2 value. Already, utility-factor adjustments are planned to start in 2025 by the European Union, and it has already been discussed that as the monitored fleet increases, those factors will be adjusted based on the observed value. The objective is procedural, not rhetorical: make compliance mathematics conform to the actual operation of vehicles, and diminish the desire to make infrequently charged PHEVs appear like near-zero-emission vehicles.

To car manufacturers, the observation by Barra is a design brief in the category of engineering and incentives. In case the plug-in functionality is a choice, the emissions results will depend on what incentives the driver to plug-in: available charging, software reminders, fleet policies, tank size, and the minimum electric potential. The absence of those levers causes the so-called “bridge” vehicle to transform into a more petrol-thirsty car with a charge port by chance.