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PHEVs emit almost 5x greater planet-heating pollution than lab-reported figures show, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy group. This contrasts sharply with lab tests, which assumed a 75% reduction in pollution.

Researchers examined information from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead researcher involved in the report. “This gap is widening and poses a serious issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric mode compared to overall distance. They determined that only 27% of travel was done in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than lab projections. That happened because electric motors were insufficiently powerful enough to operate independently, leading to engines burning fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

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

“The strong claims that manufacturers often promote about their PHEV cars are obviously far from the mark,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into political debates as automakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with large automotive industries.

Some senior officials have suggested PHEVs as a possible “compromise” option to include in the legislation.

An independent energy policy specialist, who was unaffiliated with the research, called the report a “very useful addition” after years in which parts of the car industry claimed there was too little information to properly evaluate actual emissions.

“These findings demonstrate, without question, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with utmost care and in the light of that evidence.”