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

Widening Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a non-profit organization. That differs sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts studied information from onboard fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are falling,” said a lead researcher participating in the report. “This gap is widening and creates a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to overall distance. They determined that only 27% of travel was completed in EV mode, while official estimates assumed over four-fifths.

Even, when operating in EV mode, emission amounts were significantly higher than lab projections. This happened because electric motors were insufficiently powerful enough to operate alone, resulting to engines burning fossil fuels for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled four large automaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more per year in operating expenses than is assumed under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport analyst. “Buyers are being misled 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 production, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant automotive manufacturing.

Several high-level politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the legislation.

An external energy economics specialist, who was not involved with the research, called the analysis a “highly valuable addition” after years in which segments of the car sector claimed there was too little information to accurately assess actual emissions.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of this evidence.”