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PHEVs emit almost 5x more global warming emissions than official figures indicate, as per a recent analysis.

Growing Gap Between Lab and Actual CO2 Output

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers studied data from onboard fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a lead researcher participating in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to overall mileage. The team determined that only 27% of driving was completed in electric mode, while official assumptions suggested 84%.

Additionally, when running in EV mode, emission levels were well above lab projections. That occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines burning gasoline for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four major carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would spend about €500 extra per year in running costs than is estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly way off the truth,” stated a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been brought again into political debates as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car industry and opposition from member states with significant car industries.

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

An external energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was too little information to properly evaluate real-world CO2 output.

“The results demonstrate, 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 regarding PHEVs should be made with utmost care and in the light of this data.”