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Plug-in hybrid cars produce almost 5x more planet-heating emissions than official figures indicate, according to a new report.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy organization. That contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a lead analyst involved in the study. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to total distance. The team determined that only a quarter of driving was done in electric mode, while official assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than official projections. This happened because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning gasoline for nearly one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 more per year in running costs than is assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are clearly way off the mark,” stated a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn back into political debates as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large automotive manufacturing.

Several senior politicians have proposed plug-in hybrids as a potential “compromise” option to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which parts of the automotive sector claimed there was insufficient information to properly assess actual CO2 output.

“These findings show, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “All regulatory changes concerning PHEVs should be implemented with extreme care and in the light of that data.”