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Plug-in hybrid cars emit nearly 5x more global warming emissions than lab-reported data show, according to a new report.

Widening Discrepancy In Lab and Actual Emissions

Data shows that PHEVs release only 19% less CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit organization. That differs sharply with laboratory estimates, which suggested a 75% reduction in pollution.

Analysts studied information from onboard energy use meters of eight hundred thousand cars registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” said a lead analyst involved in the report. “This gap is growing and poses a significant issue. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power relative to overall mileage. The team found that just 27% of driving was done in electric mode, while lab estimates assumed 84%.

Additionally, when operating in electric mode, emission levels were well above official projections. This happened because EV motors were insufficiently powerful enough to operate independently, resulting to combustion motors burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV emissions enabled several large automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more per year in operating costs than is assumed under lab conditions.

“The bold statements that automakers often promote about their PHEV vehicles are clearly way off the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Industry Pressure

Hybrid cars have recently been brought again into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from member states with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An independent energy policy expert, who was not involved with the research, described the analysis a “highly valuable addition” after years in which parts of the automotive sector argued there was insufficient information to accurately assess actual emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they stated. “All policy adjustments concerning PHEVs should be implemented with extreme care and in the light of that data.”