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PHEVs emit nearly five times more planet-heating emissions than lab-reported figures indicate, according to a recent report.

Widening Gap In Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, based on research carried out by a advocacy organization. That differs sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a senior researcher participating in the study. “This discrepancy is widening and poses a significant problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to overall mileage. They found that just a quarter of travel was done in EV mode, whereas official estimates suggested over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab projections. This happened because electric motors were insufficiently powerful enough to function independently, resulting to engines using gasoline for almost a third of the travel covered in electric mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra per year in operating costs than is assumed under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been brought back into political debates as carmakers have pressed the EU to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the car sector and opposition from member states with significant automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

An external energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful contribution” after years in which segments of the automotive industry claimed there was insufficient data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with extreme care and in the light of that data.”