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Plug-in hybrid cars release almost 5x more global warming pollution than lab-reported figures show, according to a new report.

Widening Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a non-profit organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a lead analyst participating in the study. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Key Factors Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric power compared to overall mileage. They determined that just a quarter of driving was done in electric mode, while official assumptions suggested over four-fifths.

Even, when running in EV mode, emission levels were well above official projections. This occurred because electric motors were not strong enough to function alone, leading to combustion motors using gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled four large automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 extra annually in operating costs than would be estimated under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Hybrid vehicles have lately been drawn again into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant car manufacturing.

Some high-level officials have proposed PHEVs as a possible “flexibility” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which parts of the automotive sector argued there was too little data to accurately assess real-world CO2 output.

“These findings show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost care and in the light of this data.”