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Plug-in hybrid electric vehicles produce almost five times more planet-heating pollution than lab-reported figures show, according to a recent report.

Growing Discrepancy In Lab and Actual CO2 Output

Data reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit organization. This differs sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use meters of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” said a lead researcher involved in the study. “That gap is growing and creates a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles driven in electric power compared to overall distance. The team determined that just a quarter of travel was completed in electric mode, while official estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than official estimates. This occurred because electric motors were not strong sufficient to operate independently, resulting to combustion motors using gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled several large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 extra annually in running costs than is estimated under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have lately been drawn again into policy debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car industry and opposition from member states with large car industries.

Several high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which segments of the automotive sector claimed there was insufficient information to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional cars,” they stated. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and considering this data.”