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Plug-in hybrid cars produce almost 5x more planet-heating emissions than lab-reported data indicate, as per a new analysis.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts sharply with lab tests, which suggested a 75% reduction in emissions.

Researchers studied information from onboard fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a lead analyst involved in the report. “That gap is growing and poses a serious issue. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to total distance. The team found that just 27% of driving was done in EV mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than lab estimates. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four major automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend about €500 extra annually in running costs than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid cars have lately been drawn again into policy discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car manufacturing.

Some senior officials have proposed PHEVs as a possible “flexibility” solution to introduce in the legislation.

An external energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after years in which segments of the automotive sector argued there was insufficient data to accurately evaluate actual emissions.

“These findings show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” they said. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and in the light of this data.”