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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating pollution than lab-reported data show, according to a new analysis.

Widening Gap In Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a non-profit group. This contrasts sharply with lab tests, which suggested a 75% decrease in emissions.

Analysts examined information from onboard fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output 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 emissions are decreasing,” said a senior researcher participating in the study. “This gap is widening and creates a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total mileage. They found that just a quarter of travel was completed in EV mode, whereas lab estimates suggested over four-fifths.

Even, when running in EV mode, emission levels were significantly higher than official estimates. That occurred because electric motors were not strong enough to operate alone, leading to combustion motors burning gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed several large carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra annually in operating expenses than would be assumed under lab conditions.

“The bold claims that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been drawn back into policy discussions as automakers have pressed the EU to relax CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant car industries.

Some high-level officials have proposed PHEVs as a possible “flexibility” option to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the automotive industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they said. “All regulatory changes regarding PHEVs should be implemented with utmost care and considering that evidence.”