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Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than lab-reported figures indicate, according to a recent analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit group. That contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Analysts examined information from onboard energy use meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are falling,” said a lead researcher involved in the study. “This gap is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Behind the Emissions Gap

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

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. That occurred because electric motors were not strong sufficient to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the distance covered in EV mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 extra annually in running expenses than would be estimated under laboratory tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little better than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political discussions as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large automotive manufacturing.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” option to include in the legislation.

An independent energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after years in which parts of the automotive industry claimed there was too little data to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “Any policy changes concerning PHEVs should be implemented with extreme care and in the light of this data.”