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PHEVs produce almost five times greater global warming emissions than lab-reported data show, as per a new report.

Widening Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit group. That differs sharply with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a lead researcher participating in the report. “That gap is widening and creates a significant issue. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to total distance. The team determined that just 27% of travel was done in electric mode, while official estimates suggested over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than official estimates. This happened because electric motors were not strong enough to function alone, resulting to engines using gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV CO2 output enabled four large carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 extra per year in running costs than would be estimated under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” commented a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been brought again into policy debates as carmakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant automotive manufacturing.

Some senior officials have suggested PHEVs as a potential “compromise” option to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which parts of the car sector claimed there was too little data to accurately evaluate actual emissions.

“The results demonstrate, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering this data.”