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PHEVs produce almost five times greater global warming pollution than lab-reported figures show, according to a recent report.

Growing Gap In Official and Real-World Emissions

Data reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit organization. That differs sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Researchers examined information from in-vehicle energy use monitors of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” said a lead researcher participating in the report. “That discrepancy is growing and poses a serious problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to total mileage. They found that only a quarter of travel was completed in EV mode, whereas official estimates suggested 84%.

Even, when running in electric mode, pollution levels were significantly higher than official projections. This happened because electric motors were not strong sufficient to operate alone, resulting to engines burning fossil fuels for nearly a third of the distance completed in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled several large automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more annually in running expenses than would be assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV cars are clearly way off the truth,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with significant car manufacturing.

Some senior officials have suggested PHEVs as a potential “flexibility” option to introduce in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable addition” after years in which segments of the car sector claimed there was too little information to accurately evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional cars,” they stated. “Any policy adjustments regarding PHEVs should be implemented with utmost care and in the light of that data.”