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Plug-in hybrid electric vehicles release almost five times more global warming emissions than lab-reported figures show, according to a new report.

Growing Gap Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a advocacy group. This differs significantly with lab tests, which assumed a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a senior researcher involved in the study. “This gap is growing and poses a serious problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery power compared to overall distance. They found that only 27% of travel was done in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution amounts were well above official estimates. That occurred because electric motors were not strong sufficient to operate independently, resulting to engines using fossil fuels for nearly a third of the distance completed in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed several large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in running costs than would be assumed under lab tests.

“The bold claims that automakers often promote about their PHEV vehicles are obviously far from the truth,” stated a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as carmakers have pressed the EU 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 EU countries with large automotive manufacturing.

Several high-level politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

An external energy policy specialist, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was too little information to accurately evaluate real-world emissions.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert stated. “All policy adjustments regarding PHEVs should be implemented with utmost caution and considering that evidence.”