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PHEVs emit almost 5x greater planet-heating emissions than lab-reported data indicate, according to a new report.

Widening Gap In Official and Real-World CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than traditional gas and diesel cars, based on research carried out by a non-profit organization. This contrasts sharply with lab tests, which suggested a 75% reduction in emissions.

Analysts examined information from onboard energy use meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a lead analyst involved in the report. “That gap is widening and poses a serious problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power compared to overall mileage. The team found that just a quarter of driving was completed in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when running in electric mode, pollution levels were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful enough to function alone, leading to combustion motors burning gasoline for nearly a third of the travel covered in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed several large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra per year in operating costs than is estimated under lab conditions.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” option to include in the regulation.

An independent energy economics expert, who was unaffiliated with the research, called the report a “very useful addition” after years in which segments of the car industry argued there was insufficient information to properly assess real-world emissions.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they said. “All policy changes concerning PHEVs should be implemented with utmost caution and considering this evidence.”