Plug-in Hybrid Cars Emit Nearly as Much as Gasoline Vehicles, Study Finds

Plug-in hybrid cars emit nearly 5x more global warming emissions than lab-reported data show, according to a recent report.

Growing Discrepancy In Lab and Actual CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy group. This contrasts significantly with lab estimates, which suggested a 75% decrease in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a lead analyst involved in the study. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as much as petrol cars.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to total distance. They found that just a quarter of travel was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. That happened because EV motors were not strong enough to function independently, leading to combustion motors burning fossil fuels for nearly a third of the travel completed in EV mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several large automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in running costs than is estimated under laboratory tests.

“The bold claims that automakers like to make about their PHEV vehicles are obviously far from the truth,” stated a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have lately been drawn again into political discussions as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large car manufacturing.

Several high-level politicians have suggested PHEVs as a potential “flexibility” solution to introduce in the regulation.

One external energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which segments of the car sector argued there was too little information to properly assess actual CO2 output.

“These findings show, without question, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be made with utmost care and considering this data.”