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Plug-in hybrid cars produce almost five times greater global warming pollution than lab-reported data indicate, according to a new analysis.

Growing Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy group. This contrasts significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” stated a senior researcher involved in the report. “That gap is widening and creates a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric power compared to overall mileage. The team found that just a quarter of travel was completed in EV mode, while official estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. That happened because electric motors were not strong enough to function independently, resulting to combustion motors using fossil fuels for almost one-third of the travel covered in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed four major carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 extra annually in running costs than would be estimated under laboratory conditions.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” stated a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been drawn back into political discussions as automakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with large automotive manufacturing.

Some senior officials have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they stated. “All regulatory changes concerning PHEVs should be made with utmost care and in the light of that evidence.”