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PHEVs produce nearly five times greater planet-heating emissions than lab-reported data indicate, according to a new analysis.

Growing Gap Between Official and Actual CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This contrasts significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers studied information from onboard energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a lead researcher participating in the study. “That gap is growing and creates a serious issue. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric power compared to total distance. The team found that only a quarter of travel was completed in EV mode, while lab estimates assumed 84%.

Even, when running in electric mode, emission levels were significantly higher than official estimates. That happened because electric motors were not strong enough to function independently, leading to engines using fossil fuels for almost a third of the distance covered in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four large automaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running expenses than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn back into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car industries.

Several high-level officials have suggested PHEVs as a potential “compromise” option to introduce in the regulation.

One independent energy policy specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which segments of the automotive industry claimed there was too little data to properly evaluate actual emissions.

“These findings show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with extreme care and considering that evidence.”