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Plug-in hybrid cars release almost 5x more global warming emissions than official figures indicate, according to a recent report.

Widening Gap Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a advocacy organization. That contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” stated a lead researcher participating in the report. “This gap is growing and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total distance. The team determined that only a quarter of travel was done in EV mode, whereas lab estimates suggested 84%.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab projections. This happened because electric motors were not strong enough to function alone, leading to engines using fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Economic Implications

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

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

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with large car manufacturing.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” solution to include in the legislation.

One independent energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which segments of the car sector claimed there was insufficient data to accurately assess actual emissions.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” they stated. “All policy adjustments concerning PHEVs should be made with utmost caution and considering this data.”