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Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than official data indicate, as per a recent report.

Growing Gap Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy group. That differs significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” said a senior researcher participating in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of miles travelled in battery power compared to total distance. They found that just a quarter of driving was completed in EV mode, while official assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were well above official projections. That happened because electric motors were not strong sufficient to function independently, leading to combustion motors burning gasoline for almost a third of the distance completed in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 more annually in running expenses than would be assumed under lab conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant automotive industries.

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

An external energy policy expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which segments of the car sector claimed there was insufficient data to accurately assess actual emissions.

“The results show, without question, that the gap between lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel cars,” the expert said. “All regulatory adjustments regarding PHEVs should be implemented with extreme care and in the light of this data.”