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Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit organization. This differs significantly with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a senior researcher participating in the study. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to overall mileage. The team found that only a quarter of travel was completed in EV mode, while official assumptions suggested over four-fifths.

Even, when operating in EV mode, emission amounts were well above lab projections. This occurred because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed four large carmaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 extra annually in running expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” stated a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been brought back into political discussions as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with significant automotive manufacturing.

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

An external energy policy expert, who was not involved with the research, called the analysis a “highly valuable addition” after years in which parts of the automotive sector argued there was too little information to accurately assess real-world CO2 output.

“The results show, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any policy changes regarding PHEVs should be made with utmost caution and in the light of this data.”