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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating emissions than lab-reported figures indicate, according to a new report.

Growing Discrepancy In Official and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel cars, based on research carried out by a non-profit group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” said a senior analyst involved in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power relative to total mileage. They found that only a quarter of travel was completed in electric mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful enough to function alone, leading to combustion motors burning fossil fuels for almost one-third of the distance covered in EV mode.

Regulatory and Economic Implications

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

Additionally, owners of PHEVs could spend approximately €500 extra annually in operating expenses than would be estimated under lab conditions.

“The strong statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought back into policy discussions as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and resistance from member states with large car manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which segments of the automotive industry argued there was too little data to accurately evaluate real-world emissions.

“These findings show, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional vehicles,” they stated. “All policy changes concerning PHEVs should be implemented with utmost care and in the light of that evidence.”