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PHEVs produce almost five times more planet-heating emissions than lab-reported figures show, according to a new report.

Widening Discrepancy In Official and Actual Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit group. This differs significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “This gap is growing and creates a serious problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode compared to overall distance. The team determined that only a quarter of travel was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than official projections. That happened because electric motors were not strong enough to function independently, resulting to engines burning gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Financial Implications

Based on calculations, the underestimation of PHEV emissions allowed several large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 more annually in running costs than is assumed under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant car industries.

Several high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy policy expert, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was too little data to properly assess actual emissions.

“These findings demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they stated. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering this evidence.”