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Plug-in hybrid cars release nearly 5x greater global warming emissions than official data show, according to a recent report.

Widening Gap In Official and Real-World Emissions

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, based on analysis conducted by a non-profit group. This differs sharply with laboratory tests, which assumed a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “That gap is widening and poses a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall distance. They determined that only 27% of travel was done in electric mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. That happened because EV motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled several major automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more annually in operating expenses than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have recently been brought again into policy discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the car industry and opposition from member states with large automotive industries.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” option to include in the legislation.

One independent energy economics expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the automotive sector argued there was insufficient information to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional cars,” they said. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”