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Plug-in hybrid cars emit nearly 5x greater global warming emissions than lab-reported data indicate, as per a new analysis.

Widening Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy group. That differs sharply with laboratory tests, which suggested a 75% reduction in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 cars sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead researcher involved in the report. “That gap is growing and poses a significant problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to overall distance. They determined that only 27% of driving was completed in EV mode, while official estimates assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above lab projections. This happened because electric motors were not strong enough to operate independently, leading to combustion motors using gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Financial Implications

Based on calculations, the underestimation of PHEV CO2 output allowed several large carmaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra per year in running costs than would be assumed under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have recently been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with significant car manufacturing.

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

An independent energy economics expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the car industry claimed there was too little information to accurately assess actual CO2 output.

“The results show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” they said. “Any regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that data.”