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PHEVs produce almost five times more global warming emissions than lab-reported figures indicate, as per a recent analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on analysis conducted by a advocacy group. That differs sharply with laboratory tests, which suggested a 75% decrease in pollution.

Researchers studied data from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” said a lead researcher involved in the report. “This gap is widening and poses a serious problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery power relative to total distance. They found that just 27% of travel was completed in electric mode, whereas lab estimates suggested 84%.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. That happened because EV motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning fossil fuels for nearly a third of the distance covered in EV mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed four large automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 extra per year in operating costs than is assumed under lab tests.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large automotive industries.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One independent energy economics expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after years in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world emissions.

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