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Plug-in hybrid cars emit almost 5x greater planet-heating emissions than lab-reported data show, according to a new report.

Widening Discrepancy In Official and Real-World Emissions

Data reveals that PHEVs release just 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. That differs sharply with lab tests, which suggested a 75% decrease in emissions.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a lead analyst participating in the report. “That gap is widening and creates a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team determined that only a quarter of driving was done in EV mode, while lab estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than official projections. This happened because EV motors were not strong sufficient to function independently, resulting to engines burning fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled several large automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 extra per year in operating costs than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant automotive industries.

Some high-level politicians have proposed plug-in hybrids as a potential “flexibility” option to include in the legislation.

One external energy policy expert, who was not involved with the study, described the analysis a “very useful contribution” after a long period in which parts of the car industry argued there was too little data to properly evaluate actual CO2 output.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “All regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”