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Plug-in hybrid cars emit almost 5x greater planet-heating pollution than lab-reported figures show, as per a new report.

Growing Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit organization. This contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 cars registered in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a lead researcher participating in the study. “That gap is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total mileage. They found that only a quarter of driving was done in EV mode, while official assumptions suggested 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were not strong enough to function alone, leading to combustion motors using fossil fuels for nearly one-third of the travel covered in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output enabled four large carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 more per year in operating costs than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some senior politicians have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the report a “very useful contribution” after a long period in which parts of the car sector claimed there was insufficient data to properly evaluate real-world emissions.

“The results demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional cars,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of this evidence.”