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Plug-in hybrid electric vehicles emit nearly 5x greater planet-heating emissions than official figures show, according to a recent report.

Growing Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit group. This differs significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers studied data from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a senior researcher involved in the report. “That gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery mode relative to total mileage. They determined that only a quarter of travel was completed in electric mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above official estimates. That happened because EV motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in electric mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more annually in operating costs than is estimated under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been brought back into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and resistance from member states with significant car industries.

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

An independent energy policy specialist, who was not involved with the research, described the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was too little information to accurately evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “All policy changes regarding PHEVs should be made with extreme care and considering that evidence.”