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

Widening Discrepancy Between Lab and Actual Emissions

Data reveals that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to research carried out by a non-profit group. This contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard fuel consumption monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a senior analyst involved in the study. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode compared to total mileage. They determined that just 27% of travel was done in electric mode, whereas official assumptions assumed 84%.

Additionally, when running in EV mode, emission amounts were well above official estimates. That occurred because electric motors were not strong sufficient to function independently, resulting to engines burning fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV emissions allowed several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in operating costs than is assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have recently been brought back into political debates as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car sector and resistance from EU countries with large automotive manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” option to include in the legislation.

An independent energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which segments of the car industry claimed there was too little information to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or conventional vehicles,” they stated. “All regulatory changes regarding PHEVs should be implemented with extreme care and in the light of that evidence.”