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Plug-in hybrid electric vehicles produce nearly 5x more global warming emissions than lab-reported data indicate, according to a new analysis.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel cars, according to analysis carried out by a non-profit organization. That contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in emissions.

Analysts examined information from onboard energy use meters of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery mode relative to total mileage. They determined that only a quarter of driving was completed in EV mode, whereas official assumptions suggested 84%.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were not strong enough to function independently, resulting to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled several large automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend about €500 more per year in operating expenses than is assumed under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into political discussions as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced intense lobbying from the car industry and resistance from member states with significant automotive industries.

Some high-level officials have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An external energy policy expert, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was insufficient information to properly assess actual emissions.

“These findings demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert said. “Any policy changes concerning PHEVs should be made with extreme care and considering this data.”