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Plug-in hybrid cars produce almost five times more planet-heating emissions than official figures show, according to a new report.

Widening Gap In Lab and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy organization. This differs sharply with lab tests, which suggested a 75% decrease in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a lead researcher involved in the study. “This discrepancy is growing and poses a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to overall mileage. The team found that only 27% of travel was completed in electric mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than lab projections. That occurred because electric motors were not strong enough to operate independently, leading to engines burning fossil fuels for nearly a third of the distance completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 more annually in running expenses than would be assumed under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been drawn again into policy discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large car manufacturing.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” option to include in the legislation.

An external energy economics expert, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the car sector claimed there was too little information to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel cars,” they said. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and considering that evidence.”