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Plug-in hybrid electric vehicles release almost 5x greater global warming pollution than official figures indicate, according to a new report.

Growing Gap In Official and Actual Emissions

Statistics shows that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, according to analysis conducted by a non-profit group. This differs sharply with lab tests, which suggested a 75% decrease in pollution.

Analysts studied data from onboard energy use meters of 800,000 cars registered in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the report. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “utility factor” – the ratio of miles driven in electric power relative to overall distance. They found that only 27% of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when running in EV mode, emission levels were significantly higher than lab estimates. This occurred because electric motors were not strong enough to operate alone, resulting to engines burning fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more per year in running costs than would be estimated under lab conditions.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large car manufacturing.

Several high-level politicians have suggested PHEVs as a potential “flexibility” solution to include in the legislation.

An independent energy economics expert, who was not involved with the study, described the report a “highly valuable 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 real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” they stated. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of that evidence.”