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Plug-in hybrid cars produce almost 5x more global warming pollution than official data show, as per a recent analysis.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, according to analysis conducted by a advocacy group. This differs sharply with lab tests, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” said a lead researcher participating in the study. “This gap is widening and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall distance. They found that just a quarter of driving was completed in electric mode, while lab assumptions suggested over four-fifths.

Even, when running in EV mode, emission amounts were well above official estimates. That occurred because electric motors were not strong sufficient to operate independently, leading to combustion motors burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed several major carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in operating costs than is assumed under lab conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles 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 environment and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large car manufacturing.

Some senior officials have suggested PHEVs as a possible “compromise” option to introduce in the regulation.

An independent energy economics expert, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which parts of the car sector claimed there was too little information to accurately evaluate real-world emissions.

“The results show, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” they said. “All regulatory changes concerning PHEVs should be implemented with utmost care and in the light of this data.”