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PHEVs produce almost five times more global warming emissions than lab-reported data show, according to a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy group. This contrasts significantly with lab estimates, which suggested a 75% decrease in pollution.

Analysts examined data from onboard energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” stated a senior analyst involved in the study. “That gap is growing and poses a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total mileage. They found that just a quarter of travel was done in EV mode, whereas official estimates suggested over four-fifths.

Additionally, when running in electric mode, emission levels were well above official estimates. That occurred because electric motors were not strong enough to operate alone, resulting to combustion motors burning fossil fuels for nearly one-third of the travel covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra per year in running costs than would be assumed under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid cars are obviously far from the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with significant car manufacturing.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, called the report a “very useful addition” after a long period in which parts of the car industry claimed there was insufficient information to accurately assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering that data.”