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

Growing Gap Between Official and Actual Emissions

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel cars, based on analysis carried out by a advocacy group. That contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a senior researcher participating in the study. “That gap is growing and creates a significant issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to total distance. The team determined that just 27% of travel was completed in EV mode, whereas official assumptions assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above official estimates. That occurred because electric motors were insufficiently powerful sufficient to function alone, leading to engines burning gasoline for almost one-third of the travel completed in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled four large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than is assumed under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the mark,” stated a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little better than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been brought again into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large automotive manufacturing.

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

An independent energy policy expert, who was not involved with the research, described the report a “highly valuable addition” after a long period in which segments of the car sector claimed there was insufficient data to accurately evaluate actual emissions.

“The results show, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” the expert said. “Any regulatory changes concerning PHEVs should be made with extreme care and considering this evidence.”