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PHEVs emit nearly five times greater global warming emissions than lab-reported figures show, according to a recent analysis.

Widening Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit group. That differs significantly with laboratory tests, which assumed a 75% reduction in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” said a senior researcher participating in the report. “That gap is growing and poses a serious problem. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power compared to overall mileage. They found that just a quarter of driving was completed in electric mode, whereas lab assumptions suggested 84%.

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

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled several major automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in operating costs than is assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have recently been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large automotive industries.

Some high-level politicians have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

An independent energy economics specialist, who was not involved with the study, called the report a “very useful contribution” after years in which segments of the car sector claimed there was too little information to properly assess actual CO2 output.

“These findings show, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert said. “Any policy adjustments concerning PHEVs should be made with utmost caution and in the light of that evidence.”