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Plug-in hybrid cars produce nearly five times greater global warming pollution than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy group. This contrasts sharply with laboratory estimates, which suggested a 75% decrease in emissions.

Researchers studied information from onboard energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a lead analyst involved in the study. “This discrepancy is widening and poses a significant problem. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery power relative to total mileage. The team determined that only a quarter of travel was completed in EV mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above official estimates. This occurred because electric motors were insufficiently powerful sufficient to operate alone, leading to combustion motors burning fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed four large automaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more per year in operating expenses than is assumed under laboratory conditions.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have pressed the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with large car industries.

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

One external energy economics expert, who was unaffiliated with the study, described the report a “highly valuable addition” after years in which segments of the automotive industry argued there was insufficient information to properly assess actual emissions.

“The results show, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “Any regulatory changes concerning PHEVs should be implemented with utmost care and considering this data.”