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PHEVs emit nearly five times greater global warming pollution than lab-reported data indicate, according to a new analysis.

Growing Gap Between Official and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. This contrasts significantly with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle energy use meters of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a senior analyst involved in the study. “That discrepancy is growing and poses a serious issue. As a result, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric power compared to overall mileage. They determined that just 27% of travel was done in electric mode, while lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were well above lab projections. That occurred because EV motors were insufficiently powerful enough to function independently, resulting to combustion motors using fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled several large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra per year in operating costs than would be assumed under lab tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant automotive manufacturing.

Several senior politicians have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the study, described the report a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to accurately assess actual emissions.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” they stated. “All policy changes concerning PHEVs should be implemented with utmost caution and considering that evidence.”