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Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than lab-reported figures show, according to a recent report.

Growing Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This differs sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a senior analyst participating in the study. “This gap is widening and creates a serious problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to overall mileage. The team found that only 27% of travel was completed in EV mode, whereas official estimates assumed 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for almost a third of the distance completed in EV mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output allowed four major automaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running expenses than is estimated under lab tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought again into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from EU countries with significant automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy economics specialist, who was not involved with the study, called the analysis a “very useful contribution” after years in which segments of the car sector claimed there was insufficient data to properly assess real-world CO2 output.

“These findings show, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel cars,” they said. “Any regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering that evidence.”