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Plug-in hybrid electric vehicles emit nearly 5x more planet-heating emissions than lab-reported data indicate, as per a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, according to research carried out by a advocacy group. That contrasts sharply with laboratory tests, which suggested a 75% reduction in emissions.

Researchers examined information from in-vehicle energy use monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a senior researcher involved in the report. “This gap is widening and poses a serious issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric mode relative to total mileage. They determined that just a quarter of travel was done in electric mode, while lab estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were well above lab estimates. That happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning fossil fuels for nearly one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV emissions allowed several large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could pay about €500 extra per year in operating costs than would be assumed under lab tests.

“The bold statements that automakers often promote about their PHEV cars are obviously way off the mark,” commented a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large automotive manufacturing.

Some senior officials have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

One external energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after a long period in which segments of the car sector claimed there was too little information to accurately assess actual emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they stated. “All policy adjustments concerning PHEVs should be implemented with extreme care and considering this data.”