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Plug-in hybrid electric vehicles emit almost 5x greater global warming emissions than lab-reported data show, according to a new analysis.

Widening Gap Between Official and Actual Emissions

Data shows that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, based on research conducted by a advocacy group. This contrasts significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Researchers studied data from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a lead researcher participating in the report. “That discrepancy is widening and poses a serious issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode compared to total distance. They found that just 27% of driving was completed in electric mode, while official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. That occurred because EV motors were insufficiently powerful sufficient to function alone, resulting to engines using fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled four major automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra per year in running expenses than would be assumed under laboratory 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 believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from member states with significant automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car sector claimed there was insufficient information to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme care and in the light of that data.”