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Plug-in hybrid electric vehicles emit almost five times greater planet-heating emissions than lab-reported data show, according to a recent analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a lead researcher participating in the study. “This gap is growing and creates a serious issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric power compared to overall distance. The team found that only a quarter of travel was done in EV mode, whereas lab estimates assumed 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were not strong enough to function alone, leading to combustion motors using gasoline for almost a third of the distance completed in electric mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV emissions allowed several major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra per year in running costs than would be estimated under laboratory tests.

“The bold claims that manufacturers often promote about their PHEV cars are obviously far from the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant car industries.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One independent energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was insufficient information to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of this data.”