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Plug-in hybrid electric vehicles release almost five times more planet-heating pollution than lab-reported data indicate, according to a recent report.

Widening Gap Between Official and Actual Emissions

Data shows that PHEVs release only 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. That contrasts sharply with laboratory tests, which suggested a 75% reduction in emissions.

Researchers examined data from onboard energy use meters of 800,000 cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a senior analyst participating in the report. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric power compared to overall mileage. The team determined that only 27% of travel was done in EV mode, whereas official estimates assumed 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors using gasoline for nearly a third of the travel completed in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four major carmaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra per year in running costs than would be assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been brought again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

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

One external energy policy expert, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which parts of the car industry claimed there was insufficient information to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with extreme care and in the light of that evidence.”