Plug-in Hybrid Cars Emit Nearly as Heavily as Gasoline Vehicles, Report Finds

Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than official data indicate, according to a recent report.

Growing Discrepancy Between Official and Real-World Emissions

Data reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. This differs significantly with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a lead analyst involved in the report. “This discrepancy is growing and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Researchers linked most of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total distance. The team found that only a quarter of driving was done in electric mode, while lab assumptions assumed 84%.

Additionally, when running in electric mode, emission levels were significantly higher than official estimates. This happened because EV motors were not strong sufficient to operate alone, leading to engines burning fossil fuels for nearly a third of the travel covered in EV mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV emissions allowed four major automaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 extra per year in operating costs than would be assumed under lab conditions.

“The strong claims that automakers often promote about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with significant car manufacturing.

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

One independent energy policy expert, who was not involved with the research, described the report a “highly valuable addition” after a long period in which segments of the car industry argued there was too little information to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “All policy adjustments regarding PHEVs should be made with extreme caution and considering that data.”