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Plug-in hybrid electric vehicles release almost 5x more global warming emissions than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy Between Official and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. That contrasts significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Researchers studied information from onboard energy use meters of 800,000 cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a senior analyst involved in the study. “That gap is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode relative to overall distance. The team found that only a quarter of travel was done in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were well above official estimates. This occurred because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using fossil fuels for almost one-third of the distance covered in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more annually in operating expenses than is estimated under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” commented a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn back into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a potential “compromise” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the research, called the report a “very useful contribution” after years in which segments of the car sector argued there was insufficient information to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that data.”