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Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than lab-reported figures indicate, according to a new report.

Growing Gap In Lab and Real-World Emissions

Data reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit group. That contrasts significantly with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied information from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a lead researcher participating in the report. “This discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total distance. The team determined that only 27% of driving was completed in electric mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above official estimates. That happened because electric motors were not strong sufficient to function independently, leading to combustion motors burning gasoline for nearly a third of the travel completed in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several major carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in operating expenses than is assumed under lab tests.

“The strong statements that automakers like to make about their PHEV vehicles are clearly far from the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid cars have lately been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant automotive industries.

Several senior officials have proposed PHEVs as a possible “compromise” solution to introduce in the legislation.

An external energy economics expert, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little data to properly assess actual emissions.

“These findings show, without question, that the difference in official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they said. “All regulatory adjustments regarding PHEVs should be made with utmost caution and considering that evidence.”