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Plug-in hybrid cars emit nearly 5x more global warming emissions than lab-reported data show, according to a recent analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research carried out by a advocacy group. That contrasts significantly with lab tests, which assumed a 75% decrease in emissions.

Researchers studied information from in-vehicle energy use meters of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a lead researcher participating in the study. “That discrepancy is widening and creates a significant problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to overall mileage. The team determined that only a quarter of driving was done in electric mode, while lab estimates suggested 84%.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. That occurred because electric motors were not strong sufficient to operate independently, leading to combustion motors using fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Economic Consequences

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

Additionally, drivers of PHEVs would pay about €500 more annually in operating expenses than would be assumed under laboratory tests.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are obviously far from the truth,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little better than standard petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been drawn back into policy debates as automakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant car manufacturing.

Some high-level officials have proposed plug-in hybrids as a potential “compromise” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the study, called the report a “very useful addition” after a long period in which segments of the automotive sector claimed there was insufficient information to accurately evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert said. “Any policy changes regarding PHEVs should be implemented with extreme care and considering this data.”