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Plug-in hybrid cars emit almost five times greater global warming pollution than official figures indicate, as per a new report.

Widening Gap Between Lab and Real-World Emissions

Data reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy group. This contrasts sharply with laboratory tests, which suggested a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption meters of 800,000 cars sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a lead researcher involved in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric mode compared to overall mileage. The team determined that just a quarter of driving was completed in EV mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, emission levels were significantly higher than lab estimates. That happened because EV motors were not strong enough to operate alone, leading to engines burning gasoline for nearly one-third of the distance completed in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled several major carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay about €500 more per year in running expenses than would be assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy debates as automakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large car industries.

Some high-level politicians have suggested PHEVs as a possible “compromise” solution to include in the legislation.

An independent energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which segments of the car industry argued there was too little data to properly assess actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and considering this data.”