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Plug-in hybrid electric vehicles release almost 5x greater global warming emissions than lab-reported figures indicate, as per a new analysis.

Growing Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, according to research carried out by a non-profit organization. That contrasts significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a lead researcher participating in the report. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power relative to total mileage. They determined that just 27% of travel was completed in electric mode, whereas official estimates suggested 84%.

Even, when running in EV mode, emission levels were well above lab estimates. That happened because EV motors were not strong sufficient to function independently, leading to engines burning fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several large carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 more per year in running expenses than is estimated under laboratory tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the truth,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large automotive industries.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One independent energy policy expert, who was unaffiliated with the research, called the analysis a “highly valuable addition” after a long period in which parts of the car sector argued there was too little information to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they said. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering this data.”