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PHEVs produce nearly 5x greater global warming pollution than official data indicate, according to a new analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy group. This contrasts sharply with lab tests, which assumed a 75% reduction in pollution.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a lead researcher involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric power relative to total mileage. The team determined that just 27% of driving was done in EV mode, whereas official estimates assumed over four-fifths.

Even, when operating in electric mode, emission levels were well above official projections. This happened because electric motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for nearly one-third of the distance covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend about €500 extra annually in running costs than is assumed under laboratory tests.

“The bold claims that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought back into political discussions as automakers have lobbied the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from member states with large automotive manufacturing.

Some senior politicians have suggested PHEVs as a possible “flexibility” option to include in the legislation.

An external energy economics expert, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which parts of the car sector claimed there was insufficient data to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “All regulatory changes concerning PHEVs should be implemented with utmost caution and considering this evidence.”