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Plug-in hybrid cars release almost five times greater planet-heating emissions than official data indicate, as per a new analysis.

Widening Gap In Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a non-profit organization. That contrasts significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a lead researcher participating in the study. “That gap is growing and poses a significant problem. As a result, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to total mileage. They found that just a quarter of driving was done in EV mode, whereas official assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were well above lab projections. That occurred because electric motors were insufficiently powerful enough to operate independently, resulting to combustion motors using fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions allowed several major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 extra per year in running costs than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV cars are clearly far from the mark,” stated a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn again into political discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car sector and resistance from member states with significant automotive industries.

Several high-level politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An independent energy policy specialist, who was not involved with the research, called the report a “very useful contribution” after a long period in which parts of the automotive industry claimed there was too little information to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme care and considering this evidence.”