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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating emissions than lab-reported data show, according to a recent analysis.

Widening Gap In Official and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy group. That contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” stated a lead analyst participating in the study. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric power compared to total distance. The team determined that only 27% of travel was completed in electric mode, whereas official estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were well above official projections. This happened because EV motors were not strong sufficient to function alone, resulting to engines using fossil fuels for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 more annually in operating costs than is assumed under laboratory conditions.

“The strong claims that automakers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have recently been brought back into political debates as automakers have pressed the European Union to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from member states with large automotive industries.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was too little information to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” they stated. “Any regulatory changes regarding PHEVs should be made with utmost care and considering this evidence.”