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Plug-in hybrid electric vehicles produce almost five times greater global warming emissions than lab-reported figures indicate, according to a new report.

Growing Discrepancy In Official and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy group. This contrasts significantly with lab estimates, which assumed a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a senior researcher participating in the report. “This gap is growing and creates a serious issue. As a result, PHEVs emit almost as much as petrol cars.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall distance. They determined that just a quarter of travel was completed in EV mode, whereas lab estimates assumed 84%.

Even, when operating in EV mode, emission amounts were significantly higher than official estimates. That happened because EV motors were not strong enough to function independently, resulting to engines using fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major carmaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more annually in operating expenses than is estimated under lab tests.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought back into political discussions as automakers have lobbied the EU to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant automotive manufacturing.

Several high-level politicians have suggested PHEVs as a potential “compromise” solution to include in the legislation.

One independent energy policy specialist, who was not involved with the research, called the analysis a “highly valuable contribution” after years in which parts of the automotive industry claimed there was insufficient information to accurately assess actual emissions.

“These findings show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “All policy changes regarding PHEVs should be implemented with extreme care and considering that data.”