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Plug-in hybrid electric vehicles release nearly five times more global warming pollution than lab-reported data indicate, as per a new analysis.

Widening Discrepancy In Official and Actual Emissions

Statistics shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit group. That contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Analysts examined data from in-vehicle energy use monitors of eight hundred thousand vehicles registered in Europe 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.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a senior researcher involved in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Behind the Discrepancy

Analysts linked most of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode compared to overall mileage. The team determined that just 27% of travel was completed in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when running in electric mode, pollution levels were well above lab estimates. That occurred because electric motors were insufficiently powerful enough to operate alone, leading to combustion motors using fossil fuels for nearly a third of the travel completed in electric mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled several major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more annually in operating costs than would be estimated under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into political debates as automakers have pressed the European Union to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large car industries.

Some high-level officials have proposed PHEVs as a potential “compromise” solution to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the research, called the report a “very useful contribution” after a long period in which segments of the automotive sector argued there was too little data to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they said. “All regulatory changes regarding PHEVs should be made with extreme care and considering this evidence.”