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Plug-in hybrid cars emit almost 5x greater global warming emissions than official data indicate, according to a recent analysis.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy group. That contrasts sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts examined data from onboard energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a lead researcher participating in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in electric power compared to total mileage. They found that only a quarter of driving was completed in EV mode, while lab estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were significantly higher than official estimates. That happened because electric motors were not strong sufficient to operate independently, resulting to engines using gasoline for nearly one-third of the distance covered in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more per year in running expenses than is assumed under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have lately been brought back into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the car sector and resistance from EU countries with significant car industries.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which segments of the car sector argued there was too little data to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “Any policy changes regarding PHEVs should be made with utmost care and in the light of this data.”