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Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than lab-reported data show, according to a new report.

Widening Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs release just 19% lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a advocacy organization. This differs significantly with lab tests, which suggested a 75% reduction in emissions.

Researchers studied information from onboard fuel consumption monitors 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 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a senior analyst involved in the study. “This gap is growing and creates a significant issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode relative to total distance. They found that just 27% of travel was completed in EV mode, whereas official assumptions assumed over four-fifths.

Even, when running in EV mode, emission levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors using gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the lowballing of PHEV emissions enabled four major carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more annually in running costs than is assumed under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV cars are obviously far from the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with significant car manufacturing.

Several senior politicians have suggested plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

An independent energy economics specialist, who was not involved with the research, called the report a “highly valuable addition” after years in which parts of the car industry argued there was insufficient information to properly evaluate actual emissions.

“These findings show, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel vehicles,” they said. “Any policy adjustments regarding PHEVs should be implemented with extreme caution and considering that evidence.”