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Plug-in hybrid electric vehicles release nearly five times greater planet-heating emissions than official data indicate, as per a new analysis.

Widening Gap In Official and Real-World Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a advocacy group. This differs significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a senior researcher involved in the study. “This gap is growing and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to total distance. They found that only a quarter of driving was done in electric mode, whereas lab assumptions suggested over four-fifths.

Even, when running in electric mode, pollution amounts were well above lab estimates. That occurred because electric motors were not strong enough to function alone, resulting to engines using fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV CO2 output enabled several large carmaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 extra per year in running expenses than is assumed under lab conditions.

“The strong claims that automakers like to make about their PHEV vehicles are clearly far from the truth,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant automotive industries.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One independent energy economics expert, who was not involved with the research, described the analysis a “very useful addition” after a long period in which parts of the automotive sector claimed there was too little information to accurately assess real-world emissions.

“These findings demonstrate, without question, that the gap in official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “All regulatory changes concerning PHEVs should be made with extreme caution and in the light of this data.”