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Plug-in hybrid electric vehicles emit nearly five times greater planet-heating pollution than lab-reported figures indicate, according to a new analysis.

Widening Gap Between Official and Real-World CO2 Output

Statistics reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, according to research carried out by a advocacy group. This differs significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Analysts studied data from onboard energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” stated a senior researcher involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to total distance. They found that only 27% of driving was completed in electric mode, while lab estimates suggested over four-fifths.

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

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra annually in operating expenses than would be estimated under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid cars have lately been brought back into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car industry and opposition from member states with large automotive industries.

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

One external energy economics specialist, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive sector argued there was too little data to accurately assess actual emissions.

“The results demonstrate, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of this data.”