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Plug-in hybrid cars produce nearly five times more planet-heating emissions than lab-reported data show, according to a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research conducted by a advocacy group. This differs significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers examined information from onboard fuel consumption meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a lead researcher participating in the study. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to overall mileage. The team determined that only 27% of travel was done in electric mode, while lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful enough to function alone, leading to engines burning fossil fuels for almost a third of the distance covered in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed several large automaker companies to escape over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra annually in operating expenses than would be assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been brought again into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” solution to include in the legislation.

An external energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the car industry argued there was insufficient information to accurately evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and considering this data.”