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Plug-in hybrid electric vehicles produce almost five times greater planet-heating emissions than lab-reported figures show, according to a recent analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy group. This contrasts sharply with lab estimates, which assumed a 75% reduction in emissions.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior researcher participating in the study. “This gap is widening and poses a serious issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery power compared to overall distance. They found that just a quarter of travel was completed in EV mode, whereas lab estimates assumed over four-fifths.

Even, when operating in electric mode, pollution amounts were well above official projections. That occurred because EV motors were not strong sufficient to operate independently, leading to engines using gasoline for almost one-third of the distance covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled four large automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating expenses than is assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with significant car manufacturing.

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

An independent energy economics expert, who was not involved with the research, described the report a “very useful contribution” after years in which parts of the car industry claimed there was insufficient information to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert said. “Any policy changes concerning PHEVs should be made with utmost caution and in the light of that data.”