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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating emissions than official figures show, according to a new report.

Widening Gap Between Lab and Actual CO2 Output

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy group. This contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Analysts studied data from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a senior researcher involved in the report. “That gap is widening and poses a significant issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to overall mileage. The team determined that just a quarter of travel was completed in EV mode, whereas official estimates assumed 84%.

Even, when running in EV mode, emission amounts were significantly higher than official estimates. That occurred because electric motors were not strong sufficient to operate alone, resulting to combustion motors using fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 extra annually in running expenses than would be assumed under laboratory conditions.

“The bold statements that automakers often promote about their PHEV vehicles are obviously way off the mark,” stated a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant car industries.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

One independent energy economics specialist, who was not involved with the research, called the analysis a “highly valuable addition” after a long period in which segments of the car industry argued there was too little information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the difference between official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and in the light of this evidence.”