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PHEVs emit almost 5x greater global warming emissions than lab-reported data indicate, as per a new report.

Growing Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit organization. That differs significantly with lab tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a senior researcher participating in the study. “That discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery power relative to total mileage. They determined that only 27% of travel was completed in electric mode, while lab assumptions suggested 84%.

Even, when operating in electric mode, pollution amounts were well above lab estimates. This happened because electric motors were not strong enough to operate independently, resulting to engines using gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled several major carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra annually in running costs than would be assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant automotive manufacturing.

Some senior politicians have proposed PHEVs as a possible “flexibility” option to introduce in the regulation.

An external energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was insufficient information to accurately assess actual emissions.

“The results demonstrate, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering that evidence.”