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Plug-in hybrid electric vehicles release almost 5x greater global warming emissions than lab-reported data show, according to a new analysis.

Widening Gap In Lab and Real-World Emissions

Statistics shows that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the report. “This gap is widening and poses a serious problem. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery mode compared to total mileage. The team found that only 27% of driving was done in EV mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were not strong sufficient to operate independently, resulting to combustion motors burning gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled several major automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more per year in operating costs than would be estimated under laboratory tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and opposition from member states with large automotive industries.

Some high-level officials have proposed plug-in hybrids as a potential “compromise” solution to include in the regulation.

An external energy economics specialist, who was unaffiliated with the study, described the report a “very useful addition” after years in which parts of the automotive industry argued there was too little information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they stated. “All policy changes regarding PHEVs should be made with utmost care and considering this evidence.”