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Plug-in hybrid electric vehicles release almost 5x more global warming pollution than official figures show, according to a new report.

Growing Gap Between Official and Actual Emissions

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy group. That differs sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a senior analyst participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to overall distance. The team determined that only 27% of travel was completed in electric mode, whereas official assumptions assumed over four-fifths.

Even, when running in electric mode, emission amounts were well above lab projections. That happened because EV motors were insufficiently powerful enough to function independently, resulting to combustion motors using fossil fuels for nearly one-third of the distance covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled several large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more per year in operating costs than would be estimated under lab conditions.

“The strong claims that automakers often promote about their PHEV vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and opposition from member states with significant automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “compromise” option to introduce in the regulation.

One external energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after years in which segments of the car sector claimed there was too little information to accurately assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they said. “Any policy adjustments concerning PHEVs should be implemented with utmost care and in the light of this data.”