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Plug-in hybrid cars produce nearly 5x greater planet-heating emissions than lab-reported data show, according to a recent report.

Growing Discrepancy Between Official and Real-World CO2 Output

Statistics reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, according to research conducted by a advocacy group. This differs significantly with laboratory tests, which assumed a 75% reduction in pollution.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” stated a lead researcher participating in the report. “This gap is growing and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power relative to total mileage. They determined that just 27% of travel was done in EV mode, while official estimates assumed 84%.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. That occurred because EV motors were not strong sufficient to operate alone, resulting to engines burning fossil fuels for almost one-third of the travel covered in electric mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output enabled four large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 extra per year in operating costs than would be estimated under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously far from the mark,” commented a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought back into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and resistance from member states with large automotive industries.

Several high-level politicians have proposed PHEVs as a potential “flexibility” solution to include in the legislation.

An independent energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which parts of the car industry argued there was too little information to properly assess real-world emissions.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional cars,” they stated. “Any policy changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”