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Plug-in hybrid cars emit nearly five times greater global warming pollution than lab-reported data indicate, as per a new report.

Growing Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs emit just 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a advocacy group. That differs sharply with lab tests, which suggested a 75% decrease in emissions.

Researchers studied information from onboard energy use monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a lead researcher involved in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to overall mileage. They found that only a quarter of driving was completed in electric mode, while official estimates assumed 84%.

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

Policy and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed several large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more per year in operating expenses than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are clearly way off the mark,” commented a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Industry Lobbying

Hybrid cars have lately been brought again into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with significant car manufacturing.

Several senior politicians have suggested PHEVs as a possible “compromise” option to introduce in the legislation.

One external energy policy specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the car sector claimed there was too little data to properly evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” they stated. “Any policy changes concerning PHEVs should be implemented with extreme care and in the light of this data.”