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Plug-in hybrid electric vehicles produce almost 5x greater global warming emissions than lab-reported figures indicate, according to a new report.

Widening Gap In Official and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit organization. That differs sharply with lab estimates, which suggested a 75% decrease in pollution.

Researchers studied information from onboard fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a senior analyst participating in the study. “That gap is widening and creates a significant problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to overall mileage. They found that just 27% of travel was completed in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, resulting to engines using fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed four large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more per year in running costs than would be assumed under laboratory conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant automotive industries.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One independent energy policy expert, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which parts of the car industry claimed there was insufficient data to accurately assess actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they said. “Any policy changes regarding PHEVs should be made with extreme care and considering this evidence.”