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PHEVs emit almost five times more planet-heating emissions than lab-reported figures indicate, according to a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy group. This contrasts sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied data from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a senior researcher participating in the report. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to overall mileage. The team found that just a quarter of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above lab estimates. That occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors burning fossil fuels for nearly a third of the distance covered in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more annually in operating expenses than is assumed under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been brought back into political debates as automakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with significant car manufacturing.

Some high-level officials have suggested plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

One external energy economics expert, who was not involved with the research, called the analysis a “very useful addition” after a long period in which parts of the automotive sector claimed there was too little information to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” they said. “Any policy adjustments regarding PHEVs should be implemented with extreme care and considering this data.”