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PHEVs release almost 5x more global warming pollution than official data show, according to a recent report.

Growing Gap In Official and Actual Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit organization. This contrasts significantly with laboratory tests, which suggested a 75% reduction in pollution.

Researchers examined information from in-vehicle energy use monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” said a lead researcher participating in the report. “This gap is growing and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery power relative to overall mileage. The team found that only 27% of travel was completed in electric mode, while lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission levels were well above lab estimates. This happened because electric motors were not strong enough to function independently, resulting to combustion motors burning fossil fuels for nearly one-third of the travel covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled four large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in operating costs than would be estimated under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been brought back into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with significant automotive industries.

Several senior officials have proposed plug-in hybrids as a possible “compromise” option to include in the regulation.

An independent energy policy expert, who was not involved with the study, described the analysis a “very useful contribution” after years in which segments of the automotive industry claimed there was too little information to accurately evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” they said. “All regulatory changes concerning PHEVs should be implemented with extreme caution and considering that data.”