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PHEVs emit nearly 5x greater global warming pollution than official figures show, according to a new report.

Growing Gap Between Official and Actual CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit organization. This contrasts sharply with lab tests, which suggested a 75% decrease in pollution.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a lead analyst participating in the study. “That discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power relative to overall distance. The team determined that just a quarter of travel was completed in electric mode, while official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above lab projections. That occurred because EV motors were not strong sufficient to function alone, resulting to engines using gasoline for almost a third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions enabled four major automaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 more per year in operating expenses than is estimated under laboratory tests.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with significant car industries.

Several senior officials have proposed plug-in hybrids as a potential “flexibility” solution to include in the legislation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which segments of the car sector argued there was insufficient data to properly evaluate actual emissions.

“The results demonstrate, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel cars,” the expert stated. “All regulatory changes regarding PHEVs should be made with utmost caution and in the light of that evidence.”