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Plug-in hybrid electric vehicles emit nearly five times more planet-heating emissions than lab-reported figures indicate, according to a recent report.

Widening Gap In Official and Real-World Emissions

Data reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a advocacy group. That differs significantly with laboratory tests, which suggested a 75% decrease in emissions.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They discovered 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 increasing, while official figures are decreasing,” stated a senior analyst participating in the study. “That discrepancy is growing and creates a serious issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to overall mileage. The team found that just a quarter of travel was done in EV mode, whereas official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, emission levels were significantly higher than official estimates. This occurred because electric motors were insufficiently powerful sufficient to function independently, leading to engines using fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled several large automaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

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

“The strong statements that automakers like to make about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large automotive industries.

Several senior politicians have proposed PHEVs as a potential “compromise” solution to include in the regulation.

An independent energy policy specialist, who was not involved with the research, described the report a “very useful contribution” after a long period in which segments of the car industry claimed there was insufficient information to properly evaluate real-world CO2 output.

“The results show, without question, that the gap between official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “Any policy changes regarding PHEVs should be made with extreme caution and considering that evidence.”