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Plug-in hybrid cars emit almost 5x greater global warming pollution than lab-reported data show, according to a recent report.

Widening Discrepancy In Lab and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy group. That differs sharply with lab estimates, which suggested a 75% reduction in pollution.

Researchers examined information from onboard energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a lead researcher involved in the study. “That discrepancy is growing and creates a significant issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to overall distance. They found that just a quarter of driving was done in electric mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than official projections. That happened because EV motors were insufficiently powerful enough to function alone, leading to engines burning gasoline for nearly a third of the travel covered in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled four large carmaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra annually in running costs than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid cars have lately been drawn again into political discussions as automakers have lobbied the EU to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with significant automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which segments of the car industry claimed there was insufficient information to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” the expert stated. “Any regulatory changes regarding PHEVs should be made with utmost care and considering that evidence.”