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Plug-in hybrid electric vehicles release nearly 5x more global warming pollution than official data indicate, according to a recent report.

Widening Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit organization. That contrasts significantly with lab estimates, which assumed a three-quarters reduction in pollution.

Researchers studied data from onboard fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “That gap is growing and creates a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to overall mileage. The team determined that just 27% of travel was done in EV mode, while official estimates suggested 84%.

Additionally, when running in EV mode, pollution levels were well above lab projections. That happened because EV motors were insufficiently powerful sufficient to operate alone, leading to combustion motors using fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 more annually in operating costs than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are clearly far from the truth,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been brought back into political discussions as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant car industries.

Several senior officials have proposed plug-in hybrids as a possible “compromise” option to include in the legislation.

An independent energy economics expert, who was not involved with the study, described the analysis a “very useful contribution” after years in which parts of the car sector argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any policy changes concerning PHEVs should be made with extreme care and considering this data.”