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Plug-in hybrid cars emit almost 5x greater planet-heating pollution than official data show, according to a new analysis.

Widening Gap Between Official and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a non-profit group. That contrasts significantly with laboratory tests, which assumed a 75% decrease in pollution.

Analysts examined information from onboard energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” stated a senior analyst involved in the report. “This discrepancy is widening and creates a significant issue. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers attributed most of the difference to overestimates of the “utility factor” – the ratio of miles driven in electric power compared to overall mileage. They found that just 27% of travel was completed in electric mode, while lab estimates assumed 84%.

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

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed several major carmaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more per year in running costs than is assumed under laboratory tests.

“The bold claims that automakers often promote about their PHEV vehicles are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Hybrid cars have recently been drawn back into political debates as automakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with large car industries.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” they stated. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering this data.”