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Plug-in hybrid cars emit nearly five times greater planet-heating pollution than official figures indicate, according to a new report.

Widening Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit organization. This differs sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a senior researcher participating in the report. “This gap is widening and poses a significant issue. As a result, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to overall mileage. The team determined that just 27% of travel was completed in electric mode, while lab assumptions suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors using gasoline for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 more annually in running costs than would be assumed under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid cars are obviously far from the mark,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have recently been brought back into political discussions as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with significant car manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the legislation.

An independent energy policy expert, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient data to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional cars,” they stated. “All policy adjustments concerning PHEVs should be made with extreme care and considering that evidence.”