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Plug-in hybrid electric vehicles produce nearly five times more planet-heating emissions than lab-reported data indicate, as per a new report.

Widening Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit group. That differs significantly with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts studied data from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a senior analyst involved in the study. “This gap is widening and creates a serious issue. As a result, PHEVs emit almost as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total mileage. They determined that only 27% of driving was done in electric mode, whereas official estimates assumed 84%.

Even, when operating in EV mode, pollution amounts were well above lab projections. This occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to engines burning fossil fuels for almost one-third of the travel covered in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled four major automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

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

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with significant car manufacturing.

Several senior officials have proposed plug-in hybrids as a possible “compromise” option to include in the regulation.

An external energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which parts of the automotive industry argued there was insufficient information to properly assess actual CO2 output.

“These findings show, without question, that the difference in lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or diesel cars,” the expert said. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of that data.”