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Plug-in hybrid electric vehicles produce almost five times more planet-heating emissions than official data show, according to a recent report.

Widening Gap In Lab and Actual CO2 Output

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel cars, based on research carried out by a advocacy organization. That differs sharply with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts examined data from in-vehicle energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” said a lead analyst participating in the report. “That gap is growing and poses a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to overall distance. The team determined that only a quarter of travel was done in EV mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above official estimates. This happened because EV motors were not strong sufficient to function independently, resulting to combustion motors burning gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV emissions enabled several large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could spend about €500 more per year in running expenses than would be assumed under lab tests.

“The strong claims that manufacturers often promote about their PHEV vehicles are clearly far from the truth,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought again into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car manufacturing.

Several senior officials have proposed PHEVs as a potential “compromise” option to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little information to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” they stated. “Any policy changes regarding PHEVs should be implemented with extreme caution and considering that evidence.”