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Plug-in hybrid electric vehicles produce almost 5x more planet-heating pollution than official data show, as per a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy organization. That differs sharply with lab estimates, which assumed a 75% decrease in emissions.

Analysts examined data from onboard energy use meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” said a senior researcher involved in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric power relative to overall mileage. The team found that only 27% of travel was done in electric mode, while official estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution levels were significantly higher than official projections. That happened because electric motors were not strong enough to function alone, resulting to combustion motors using gasoline for nearly a third of the travel covered in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed several major carmaker companies to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 more annually in operating expenses than would be assumed under laboratory tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car manufacturing.

Several high-level politicians have suggested PHEVs as a possible “compromise” solution to introduce in the legislation.

An independent energy policy specialist, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was too little information to properly evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional vehicles,” they stated. “Any regulatory changes concerning PHEVs should be made with utmost care and in the light of that evidence.”