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PHEVs emit nearly 5x greater planet-heating pollution than lab-reported figures indicate, as per a new analysis.

Widening Discrepancy Between Official and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research carried out by a advocacy group. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Analysts examined information from onboard fuel consumption monitors of 800,000 cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a senior researcher participating in the study. “That discrepancy is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to overall mileage. They found that just 27% of driving was completed in electric mode, while official estimates suggested over four-fifths.

Even, when running in EV mode, pollution amounts were well above lab projections. This occurred because electric motors were not strong enough to operate alone, leading to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled four major carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 more per year in operating costs than would be assumed under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have lately been brought back into political debates as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant car manufacturing.

Several senior politicians have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the study, described the report a “very useful addition” after a long period in which parts of the automotive sector argued there was too little information to properly evaluate actual CO2 output.

“The results show, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional vehicles,” the expert said. “All regulatory changes regarding PHEVs should be made with utmost care and considering this evidence.”