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PHEVs emit nearly 5x greater planet-heating pollution than lab-reported figures show, according to a new analysis.

Widening Gap Between Lab and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy group. This differs significantly with lab tests, which suggested a 75% reduction in pollution.

Analysts studied data from onboard fuel consumption meters of eight hundred thousand cars sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a lead researcher involved in the study. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in electric mode relative to total distance. The team found that just a quarter of driving was done in electric mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab estimates. This occurred because EV motors were not strong enough to operate alone, leading to engines burning gasoline for almost a third of the distance covered in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed four large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra per year in operating costs than would be assumed under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have lately been brought again into political debates as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with large car manufacturing.

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

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

“The results demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” the expert said. “All policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of that data.”