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Plug-in hybrid cars emit nearly 5x greater planet-heating emissions than lab-reported figures show, as per a new analysis.

Widening Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a advocacy organization. That differs significantly with lab tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a senior analyst participating in the report. “That discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to overall mileage. They determined that just 27% of driving was completed in EV mode, while official estimates assumed 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors using fossil fuels for nearly one-third of the distance covered in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four major carmaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra per year in operating expenses than is assumed under lab conditions.

“The bold claims that automakers like to make about their PHEV vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and resistance from member states with significant car manufacturing.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy policy specialist, who was not involved with the research, called the report a “very useful addition” after a long period in which parts of the car sector claimed there was too little data to properly assess actual emissions.

“These findings show, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of this evidence.”