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Plug-in hybrid electric vehicles produce nearly 5x greater global warming pollution than lab-reported data show, according to a recent report.

Growing Gap Between Lab and Actual Emissions

Data reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy organization. That contrasts sharply with lab estimates, which suggested a 75% reduction in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a lead analyst involved in the study. “This gap is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in battery power compared to total mileage. They found that just a quarter of driving was completed in EV mode, while lab estimates assumed 84%.

Even, when running in electric mode, emission levels were well above lab estimates. That occurred because electric motors were insufficiently powerful enough to function independently, leading to engines burning gasoline for almost a third of the distance covered in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled four major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra annually in operating expenses than is estimated under lab conditions.

“The bold statements that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” commented a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have recently been brought back into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large automotive manufacturing.

Several senior politicians have proposed PHEVs as a possible “compromise” option to include in the regulation.

An external energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which segments of the car sector claimed there was too little data to accurately assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and considering that evidence.”