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Plug-in hybrid electric vehicles produce nearly five times greater planet-heating pollution than lab-reported data indicate, according to a new report.

Growing Gap Between Lab and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than traditional gas and diesel cars, based on analysis carried out by a advocacy organization. This contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Analysts studied information from onboard fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “This gap is growing and poses a serious issue. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total distance. They determined that just a quarter of driving was completed in electric mode, whereas lab estimates assumed 84%.

Additionally, when operating in electric mode, emission levels were well above official estimates. That happened because electric motors were insufficiently powerful enough to function independently, leading to combustion motors using fossil fuels for almost a third of the distance covered in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more annually in running expenses than is estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the truth,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car industries.

Several senior officials have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

One independent energy economics specialist, who was not involved with the study, described the report a “very useful addition” after a long period in which segments of the car industry argued there was insufficient data to properly assess real-world emissions.

“These findings show, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert stated. “All policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of this data.”