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Plug-in hybrid cars release almost five times greater global warming pollution than official data indicate, according to a recent analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit organization. This differs sharply with laboratory tests, which suggested a 75% decrease in pollution.

Analysts examined information from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a lead researcher participating in the study. “That discrepancy is widening and creates a significant issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to total mileage. They found that only 27% of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Even, when operating in EV mode, pollution amounts were well above official projections. This occurred because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning gasoline for nearly a third of the travel completed in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV emissions enabled several major carmaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

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

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into political discussions as carmakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant automotive industries.

Some high-level politicians have proposed PHEVs as a possible “flexibility” option to include in the regulation.

One independent energy policy expert, who was not involved with the research, described the analysis a “very useful contribution” after years in which segments of the automotive industry argued there was insufficient data to properly evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and considering this evidence.”