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Plug-in hybrid cars emit almost 5x greater planet-heating pollution than official data indicate, according to a new analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit group. This contrasts significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a lead researcher involved in the report. “That gap is widening and creates a serious problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric power compared to overall mileage. They determined that just 27% of travel was done in electric mode, whereas official estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful enough to function independently, leading to engines using fossil fuels for almost one-third of the distance covered in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra per year in running costs than is estimated under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from member states with significant car manufacturing.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

One external energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which parts of the car sector argued there was too little information to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” the expert said. “Any regulatory changes concerning PHEVs should be made with utmost care and considering that evidence.”