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Plug-in hybrid cars produce almost five times greater planet-heating pollution than official data indicate, according to a new analysis.

Widening Discrepancy Between Official and Actual CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit group. This contrasts significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 cars sold in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a senior researcher participating in the report. “This gap is widening and creates a significant problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total mileage. The team determined that only a quarter of travel was done in EV mode, while lab estimates suggested over four-fifths.

Even, when running in EV mode, pollution levels were significantly higher than official estimates. This happened because electric motors were not strong sufficient to function independently, leading to engines burning gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed several large automaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 extra per year in running costs than is assumed under lab conditions.

“The strong statements that automakers like to make about their PHEV vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Industry Pressure

Hybrid cars have recently been brought back into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large car manufacturing.

Several senior officials have suggested PHEVs as a potential “compromise” option to introduce in the legislation.

An external energy policy expert, who was not involved with the study, described the report a “very useful contribution” after a long period in which parts of the car sector argued there was too little information to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” they said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that data.”