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PHEVs produce almost 5x more planet-heating pollution than lab-reported data show, according to a new report.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release just 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit group. That differs sharply with laboratory tests, which assumed a 75% decrease in emissions.

Analysts studied data from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” stated a lead analyst participating in the study. “This gap is widening and creates a serious issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team determined that only a quarter of travel was completed in electric mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, pollution amounts were well above lab estimates. This occurred because EV motors were not strong sufficient to operate alone, leading to combustion motors using fossil fuels for almost a third of the travel covered in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in operating costs than is estimated under lab conditions.

“The bold claims that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” stated a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into political discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with significant automotive industries.

Some senior politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the research, described the report a “very useful addition” after years in which segments of the automotive industry claimed there was too little information to accurately evaluate actual CO2 output.

“The results show, without question, that the gap in lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel vehicles,” the expert stated. “Any regulatory changes regarding PHEVs should be made with extreme care and considering that evidence.”