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Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than lab-reported data show, as per a new report.

Widening Gap In Official and Real-World Emissions

Data shows that PHEVs emit only 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit organization. That differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from onboard energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” said a senior researcher participating in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to overall mileage. The team found that just a quarter of travel was done in EV mode, whereas official estimates suggested 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than official estimates. This happened because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions allowed four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more per year in operating costs than is estimated under laboratory tests.

“The strong claims that manufacturers like to make about their PHEV cars are obviously far from the mark,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant automotive industries.

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

One independent energy policy expert, who was unaffiliated with the study, described the report a “very useful contribution” after years in which parts of the car sector argued there was insufficient data to accurately assess actual CO2 output.

“These findings show, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and considering that data.”