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Plug-in hybrid electric vehicles emit nearly five times more global warming emissions than official data show, according to a new report.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. That contrasts sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “That gap is widening and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Behind the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to overall distance. The team determined that just 27% of travel was completed in electric mode, while lab estimates suggested over four-fifths.

Even, when running in EV mode, pollution levels were well above lab projections. That occurred because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines using gasoline for almost a third of the distance covered in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 extra per year in operating expenses than would be assumed under lab tests.

“The strong statements that automakers like to make about their PHEV vehicles are clearly far from the truth,” stated a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn back into political discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with significant car manufacturing.

Several high-level officials have proposed plug-in hybrids as a possible “flexibility” option to include in the regulation.

One external energy policy expert, who was not involved with the study, described the report a “very useful addition” after a long period in which parts of the automotive industry argued there was too little information to accurately assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” the expert stated. “Any policy changes regarding PHEVs should be implemented with extreme care and considering this evidence.”