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Plug-in hybrid cars produce nearly five times greater global warming emissions than official data indicate, according to a recent analysis.

Widening Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs release just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied information from onboard energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while official figures are falling,” stated a senior analyst involved in the study. “This discrepancy is growing and creates a significant issue. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total distance. The team determined that just a quarter of driving was completed in electric mode, whereas lab estimates assumed over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. This occurred because EV motors were not strong enough to function independently, resulting to engines using gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed several major carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more per year in operating costs than would be estimated under laboratory conditions.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been drawn again into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car manufacturing.

Some senior officials have proposed PHEVs as a potential “flexibility” solution to introduce in the legislation.

One independent energy policy expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which parts of the car sector claimed there was insufficient information to properly evaluate real-world CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” the expert said. “All policy changes concerning PHEVs should be implemented with extreme care and in the light of this data.”