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PHEVs release almost 5x greater planet-heating pollution than official data indicate, according to a new report.

Widening Discrepancy Between Official and Real-World Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, based on research carried out by a non-profit organization. This contrasts significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand vehicles registered 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 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” stated a lead researcher involved in the study. “That gap is growing and poses a serious problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power compared to overall distance. They determined that just a quarter of travel was done in electric mode, whereas official estimates suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful sufficient to function alone, leading to engines burning fossil fuels for almost one-third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 more per year in operating costs than would be assumed under laboratory conditions.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been brought again into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant automotive industries.

Several senior politicians have suggested PHEVs as a possible “compromise” solution to include in the legislation.

An independent energy policy expert, who was not involved with the research, called the report a “very useful contribution” after years in which parts of the car sector argued there was too little information to properly evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional vehicles,” they stated. “Any policy adjustments regarding PHEVs should be implemented with utmost care and considering this data.”