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Plug-in hybrid cars emit almost 5x more global warming pollution than official figures show, according to a new report.

Widening Gap Between Official and Actual CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy group. This differs sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts studied information from in-vehicle energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “This gap is widening and poses a significant problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Factors Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery power relative to total mileage. They found that just 27% of driving was completed in EV mode, whereas lab estimates assumed 84%.

Additionally, when operating in EV mode, emission levels were well above lab projections. That occurred because EV motors were insufficiently powerful enough to function alone, leading to combustion motors using fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed several large automaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more per year in running expenses than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Hybrid cars have recently been drawn again into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant automotive industries.

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

An external energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which segments of the car industry argued there was too little data to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”