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Plug-in hybrid cars release nearly five times greater planet-heating emissions than lab-reported figures show, according to a recent report.

Widening Gap Between Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel cars, according to research conducted by a non-profit organization. That differs sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts examined information from onboard fuel consumption monitors of 800,000 cars sold in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” stated a lead analyst participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to total mileage. The team determined that just 27% of travel was done in electric mode, while lab estimates suggested 84%.

Even, when operating in electric mode, emission amounts were well above lab estimates. This occurred because electric motors were insufficiently powerful enough to function independently, leading to combustion motors burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output allowed several major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more per year in operating costs than would be assumed under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been drawn again into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy policy expert, who was not involved with the research, described the report a “very useful contribution” after years in which segments of the automotive sector argued there was insufficient information to properly assess real-world CO2 output.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”