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

Widening Gap Between Official and Real-World Emissions

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy organization. This contrasts significantly with lab tests, which suggested a 75% decrease in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “This discrepancy is widening and creates a significant issue. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery power relative to total mileage. They found that just 27% of travel was done in electric mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab projections. This occurred because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using fossil fuels for nearly a third of the travel covered in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed four major carmaker groups to escape over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra annually in running costs than is assumed under lab tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the mark,” stated a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been brought again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large car manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

An independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after years in which parts of the car industry claimed there was too little information to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” they stated. “Any policy changes concerning PHEVs should be implemented with extreme caution and in the light of this evidence.”