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Plug-in hybrid cars release nearly 5x more global warming pollution than lab-reported data show, as per a new report.

Growing Discrepancy Between Official and Actual Emissions

Data reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy organization. That differs sharply with laboratory tests, which assumed a 75% decrease in emissions.

Analysts examined information from in-vehicle energy use 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 nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” said a senior analyst participating in the report. “This gap is growing and creates a significant problem. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric power relative to total mileage. They determined that only a quarter of travel was done in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission levels were well above official projections. That occurred because electric motors were insufficiently powerful enough to function independently, leading to combustion motors burning fossil fuels for nearly a third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled several large automaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more annually in operating expenses than is estimated under laboratory tests.

“The bold claims that automakers like to make about their PHEV cars are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been brought again into political discussions as carmakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the study, described the analysis a “very useful addition” after a long period in which parts of the automotive industry claimed there was insufficient data to properly assess actual emissions.

“These findings show, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with utmost care and considering that evidence.”