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

Growing Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. That contrasts sharply with lab tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a senior analyst participating in the report. “This discrepancy is widening and poses a significant problem. As a result, PHEVs emit nearly as much as petrol cars.”

Key Reasons Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery power compared to total distance. The team found that just 27% of travel was done in electric mode, whereas lab estimates suggested over four-fifths.

Even, when running in EV mode, emission levels were well above official projections. This happened because EV motors were not strong sufficient to operate independently, leading to combustion motors using gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed several large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 more per year in operating expenses than is assumed under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant car industries.

Some high-level politicians have proposed plug-in hybrids as a potential “flexibility” solution to include in the regulation.

One independent energy policy specialist, who was not involved with the research, described the analysis a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient information to properly assess actual emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with extreme care and considering that evidence.”