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Plug-in hybrid cars emit almost 5x greater global warming emissions than lab-reported figures show, according to a recent report.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit organization. This differs significantly with lab tests, which suggested a three-quarters reduction in emissions.

Analysts studied data from onboard energy use meters of eight hundred thousand cars sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” said a lead researcher participating in the study. “This gap is widening and poses a serious problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric power compared to overall mileage. The team determined that only 27% of travel was completed in electric mode, while official estimates assumed 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors burning gasoline for almost a third of the travel covered in EV mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running costs than is assumed under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One independent energy economics specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which segments of the car industry argued there was too little data to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” the expert said. “All regulatory adjustments regarding PHEVs should be made with extreme caution and in the light of that evidence.”