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Plug-in hybrid cars release almost five times greater planet-heating emissions than lab-reported figures show, as per a new analysis.

Growing Gap Between Official and Actual CO2 Output

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a non-profit group. This differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the report. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to total mileage. They determined that only 27% of travel was done in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than official projections. This occurred because EV motors were not strong enough to function alone, resulting to combustion motors using gasoline for nearly one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend about €500 extra annually in running costs than is estimated under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from member states with significant car manufacturing.

Several senior officials have proposed plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the automotive industry argued there was too little information to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” they said. “All policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”