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Plug-in hybrid cars release nearly 5x greater planet-heating emissions than lab-reported data indicate, according to a recent report.

Widening Discrepancy In Lab and Actual CO2 Output

Statistics reveals that PHEVs release just 19% less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit organization. This differs sharply with laboratory tests, which assumed a 75% reduction in pollution.

Analysts studied data from onboard energy use monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the report. “That discrepancy is widening and creates a significant problem. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to total distance. The team found that just a quarter of driving was done in EV mode, whereas official estimates assumed 84%.

Even, when running in EV mode, pollution levels were well above official estimates. This occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to combustion motors burning fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV emissions allowed several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more annually in operating expenses than is assumed under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV cars are obviously way off the truth,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from member states with significant car manufacturing.

Some high-level politicians have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

An independent energy economics specialist, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was too little information to accurately evaluate actual emissions.

“The results show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they stated. “Any regulatory changes regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”