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Plug-in hybrid cars produce nearly 5x more global warming emissions than official data show, according to a new analysis.

Growing Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit group. That differs sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts studied data from onboard energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “This discrepancy is growing and poses a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power compared to total distance. The team found that only 27% of driving was completed in electric mode, whereas lab estimates assumed over four-fifths.

Even, when running in EV mode, emission amounts were well above official projections. That occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to engines using gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed several large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than would be assumed under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant automotive industries.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An independent energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after a long period in which parts of the car industry argued there was too little information to properly assess actual CO2 output.

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