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PHEVs release nearly 5x more global warming pollution than official data indicate, according to a new report.

Growing Discrepancy Between Official and Actual CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy organization. This differs significantly with lab tests, which assumed a 75% reduction in emissions.

Researchers studied data from onboard energy use meters of 800,000 vehicles sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a lead researcher participating in the study. “This discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to total mileage. The team found that only a quarter of driving was done in EV mode, while official assumptions assumed 84%.

Even, when operating in EV mode, pollution amounts were well above official estimates. This happened because EV motors were insufficiently powerful sufficient to function independently, resulting to engines burning gasoline for nearly one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 extra annually in running costs than is assumed under lab conditions.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been brought back into political debates as carmakers have pressed the EU to weaken CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with large automotive industries.

Some high-level politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the regulation.

An independent energy economics expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive sector argued there was too little information to properly evaluate real-world emissions.

“The results show, without question, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy changes concerning PHEVs should be implemented with extreme care and considering this evidence.”