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PHEVs emit nearly five times more planet-heating emissions than lab-reported data show, as per a new analysis.

Growing Gap Between Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on analysis carried out by a advocacy group. That contrasts sharply with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a lead analyst involved in the report. “That gap is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric power relative to overall mileage. They determined that only a quarter of travel was done in electric mode, while lab assumptions assumed over four-fifths.

Even, when operating in electric mode, emission levels were well above official estimates. That happened because electric motors were not strong sufficient to function independently, resulting to engines burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra annually in running expenses than is estimated under lab tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “compromise” solution to include in the regulation.

One external energy economics specialist, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive sector argued there was insufficient data to properly assess real-world emissions.

“These findings show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional cars,” they said. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of this evidence.”