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Plug-in hybrid electric vehicles produce nearly 5x more global warming emissions than lab-reported figures indicate, as per a new analysis.

Growing Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, based on research carried out by a non-profit organization. That differs sharply with lab estimates, which suggested a 75% decrease in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” stated a senior researcher involved in the study. “That discrepancy is widening and creates a significant problem. As a result, PHEVs emit almost as much as petrol cars.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery power compared to total mileage. They found that only 27% of travel was completed in EV mode, while official estimates suggested 84%.

Additionally, when running in electric mode, pollution amounts were well above official projections. This happened because electric motors were insufficiently powerful enough to operate alone, leading to combustion motors burning gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed several major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 more per year in running expenses than is estimated under laboratory conditions.

“The strong claims that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” commented a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have pressed the European Union to relax CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to include in the legislation.

One independent energy economics specialist, who was unaffiliated with the study, described the report a “very useful addition” after a long period in which segments of the car industry claimed there was insufficient information to accurately assess actual CO2 output.

“The results demonstrate, without question, that the difference in lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional vehicles,” they stated. “All policy changes concerning PHEVs should be implemented with extreme care and in the light of this data.”