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Plug-in hybrid electric vehicles produce almost 5x more planet-heating emissions than official data indicate, as per a new analysis.

Growing Gap In Official and Actual CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That differs significantly with lab tests, which suggested a three-quarters decrease in pollution.

Analysts studied data from in-vehicle energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a senior researcher involved in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery power compared to total distance. The team found that only a quarter of travel was done in EV mode, while lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab estimates. This occurred because EV motors were insufficiently powerful sufficient to function alone, resulting to engines burning fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output enabled several major automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

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

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Hybrid cars have recently been drawn back into political discussions as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant car industries.

Several high-level politicians have suggested plug-in hybrids as a possible “compromise” option to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the study, described the analysis a “very useful contribution” after a long period in which parts of the automotive industry argued there was too little data to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the difference between lab and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they said. “Any regulatory changes regarding PHEVs should be implemented with extreme care and considering that data.”