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Plug-in hybrid cars emit almost five times greater planet-heating pollution than lab-reported data indicate, as per a new analysis.

Growing Discrepancy In Official and Real-World Emissions

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a non-profit organization. This contrasts sharply with laboratory tests, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” stated a senior researcher participating in the report. “That gap is growing and creates a serious problem. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total mileage. The team found that just 27% of travel was completed in EV mode, while official estimates suggested 84%.

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. That occurred because electric motors were not strong enough to function alone, resulting to engines using gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed four large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 extra annually in running expenses than is assumed under laboratory conditions.

“The strong statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the automotive industry and resistance from member states with large automotive industries.

Several high-level officials have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

An independent energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which segments of the car industry argued there was too little data to properly assess real-world emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional vehicles,” they said. “Any policy adjustments concerning PHEVs should be made with utmost care and in the light of this evidence.”