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Plug-in hybrid cars produce nearly 5x greater global warming emissions than lab-reported data show, according to a recent analysis.

Widening Discrepancy Between Lab and Actual CO2 Output

Data reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, according to research conducted by a advocacy group. This differs significantly with lab estimates, which suggested a 75% decrease in pollution.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” said a senior researcher participating in the report. “That gap is growing and poses a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to total mileage. They found that only 27% of travel was completed in EV mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution amounts were well above lab estimates. That happened because electric motors were not strong enough to operate independently, leading to engines burning gasoline for nearly a third of the travel completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four large automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 more per year in running expenses than is assumed under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with significant automotive manufacturing.

Several senior officials have proposed plug-in hybrids as a potential “flexibility” solution to include in the legislation.

One independent energy policy expert, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the automotive sector claimed there was insufficient information to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with utmost care and considering that evidence.”