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Plug-in hybrid cars release almost five times more global warming emissions than lab-reported data indicate, according to a new report.

Growing Discrepancy Between Lab and Actual Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit organization. That contrasts significantly with lab tests, which assumed a three-quarters decrease in pollution.

Analysts studied information from onboard fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are falling,” said a senior researcher participating in the report. “That gap is widening and poses a serious issue. As a result, PHEVs emit almost as heavily as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric power compared to total distance. The team found that just a quarter of travel was done in electric mode, while lab assumptions suggested over four-fifths.

Even, when running in electric mode, emission levels were well above official projections. This happened because electric motors were insufficiently powerful enough to operate independently, leading to engines using gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several large carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 extra per year in running expenses than is estimated under laboratory conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant automotive industries.

Some high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One independent energy economics specialist, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient data to properly evaluate real-world emissions.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “Any policy changes concerning PHEVs should be made with utmost care and considering that evidence.”