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Plug-in hybrid cars release almost 5x more global warming emissions than official figures indicate, according to a new report.

Growing Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy organization. That contrasts significantly with lab tests, which suggested a 75% reduction in pollution.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a senior researcher involved in the report. “This gap is widening and creates a significant problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in battery mode compared to overall distance. They determined that only a quarter of driving was completed in EV mode, while official estimates suggested 84%.

Additionally, when running in EV mode, pollution amounts were significantly higher than official estimates. That happened because electric motors were not strong enough to operate alone, leading to combustion motors burning fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV emissions allowed four major carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

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

“The strong statements that automakers often promote about their PHEV cars are clearly far from the mark,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought again into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with significant car manufacturing.

Some senior politicians have suggested PHEVs as a possible “flexibility” option to include in the regulation.

An independent energy policy expert, who was unaffiliated with the research, described the report a “very useful contribution” after a long period in which parts of the car industry claimed there was insufficient data to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional vehicles,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with extreme caution and considering this evidence.”