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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating emissions than official figures indicate, according to a new report.

Growing Gap Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit organization. That differs sharply with lab estimates, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a senior researcher involved in the study. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall distance. The team found that only 27% of travel was done in electric mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were well above lab projections. This happened because EV motors were not strong sufficient to function independently, resulting to combustion motors burning gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the lowballing of PHEV emissions allowed four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

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

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously far from the truth,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive industries.

Several high-level politicians have proposed PHEVs as a possible “compromise” option to include in the legislation.

One external energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after years in which parts of the car sector argued there was too little information to accurately assess actual CO2 output.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” they said. “All regulatory changes regarding PHEVs should be made with extreme caution and in the light of this data.”