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Plug-in hybrid electric vehicles emit nearly 5x greater planet-heating pollution than official data show, as per a recent report.

Growing Discrepancy In Lab and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy group. This differs significantly with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 vehicles registered in the EU from 2021 and 2023. They found that real-world 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 CO2 output are increasing, while lab-reported figures are decreasing,” said a lead researcher involved in the report. “That discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode compared to overall mileage. The team found that just 27% of driving was completed in EV mode, while lab assumptions assumed 84%.

Even, when running in EV mode, pollution levels were well above lab projections. This occurred because electric motors were not strong sufficient to operate independently, resulting to engines burning gasoline for almost a third of the distance covered in EV mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more per year in operating costs than would be estimated under laboratory conditions.

“The strong claims that automakers often promote about their PHEV vehicles are clearly far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with significant car manufacturing.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which parts of the car sector claimed there was too little data to properly evaluate real-world CO2 output.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” the expert stated. “All regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of this data.”