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PHEVs emit almost five times greater global warming emissions than lab-reported data show, according to a new report.

Growing Gap In Lab and Real-World Emissions

Data reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a advocacy group. That differs significantly with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts examined data from onboard energy use monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” stated a senior researcher participating in the study. “That discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery mode relative to overall distance. The team determined that just 27% of travel was completed in EV mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than official projections. This happened because electric motors were not strong enough to function independently, resulting to engines burning fossil fuels for almost a third of the travel completed in EV mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed several large automaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could pay about €500 extra per year in running expenses than would be estimated under laboratory tests.

“The bold statements that manufacturers like to make about their PHEV vehicles are obviously far from the mark,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Hybrid cars have lately been drawn again into political debates as automakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with significant car industries.

Some high-level politicians have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

An independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was too little data to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”