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Plug-in hybrid electric vehicles emit almost five times more planet-heating emissions than official figures indicate, according to a recent report.

Widening Gap Between Lab and Actual Emissions

Data shows that PHEVs release just one-fifth less CO₂ than conventional gas and diesel cars, according to research conducted by a advocacy group. This differs significantly with lab tests, which suggested a 75% decrease in emissions.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” said a lead researcher participating in the report. “That discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery mode compared to total distance. They determined that only 27% of travel was completed in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above lab estimates. That occurred because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning gasoline for almost a third of the distance covered in EV mode.

Policy and Economic Consequences

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

Furthermore, owners of PHEVs would spend approximately €500 more per year in running costs than is estimated under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from member states with significant car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “compromise” option to include in the legislation.

One independent energy economics expert, who was not involved with the study, described the report a “very useful addition” after years in which segments of the car industry claimed there was insufficient data to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with extreme care and in the light of this data.”