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Plug-in hybrid cars emit almost 5x greater global warming pollution than official figures show, according to a new analysis.

Growing Discrepancy Between Lab and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a advocacy organization. This contrasts sharply with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts studied data from onboard energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” stated a lead analyst involved in the study. “This discrepancy is widening and poses a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery power relative to overall mileage. They determined that just a quarter of travel was completed in EV mode, while official assumptions assumed over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. This happened because electric motors were not strong sufficient to function alone, resulting to engines using gasoline for nearly a third of the travel covered in electric mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV emissions enabled four major carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra per year in operating expenses than is assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously far from the mark,” stated a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from member states with significant automotive manufacturing.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An external energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was too little information to properly evaluate actual CO2 output.

“The results show, without question, that the gap in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or diesel cars,” they said. “All policy adjustments concerning PHEVs should be implemented with utmost caution and considering that data.”