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Plug-in hybrid electric vehicles produce almost five times more global warming emissions than lab-reported data show, according to a new report.

Widening Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a advocacy group. This differs sharply with lab estimates, which assumed a 75% decrease in emissions.

Researchers examined information from onboard energy use monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a lead researcher involved in the report. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric power relative to total mileage. The team determined that only a quarter of driving was done in EV mode, whereas lab assumptions suggested 84%.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. This occurred because electric motors were not strong sufficient to function alone, resulting to combustion motors using fossil fuels for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several major automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in operating costs than is assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “compromise” option to introduce in the regulation.

One external energy policy expert, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which parts of the automotive industry argued there was too little information to accurately assess real-world emissions.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with extreme caution and considering this data.”