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Plug-in hybrid electric vehicles emit nearly five times more planet-heating emissions than lab-reported figures show, as per a new analysis.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to research carried out by a advocacy group. This contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in emissions.

Analysts examined information from in-vehicle energy use monitors of 800,000 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, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs emit almost as much as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to total distance. The team found that just 27% of travel was completed in electric mode, while lab assumptions assumed over four-fifths.

Even, when running in EV mode, emission levels were significantly higher than lab projections. That occurred because EV motors were not strong enough to operate alone, resulting to combustion motors burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed four large carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 extra annually in running expenses than is assumed under lab conditions.

“The bold claims that automakers often promote about their PHEV vehicles are obviously way off the mark,” stated a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been brought again into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant car industries.

Some high-level officials have suggested PHEVs as a possible “flexibility” option to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which segments of the automotive sector argued there was insufficient data to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy changes regarding PHEVs should be implemented with extreme care and in the light of this evidence.”