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

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. This differs significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” said a senior analyst participating in the report. “This discrepancy is growing and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to overall distance. The team found that only a quarter of driving was done in electric mode, while official assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were well above official estimates. This happened because electric motors were insufficiently powerful enough to function alone, resulting to combustion motors using fossil fuels for almost one-third of the travel covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four large carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 extra annually in running expenses than is estimated under laboratory tests.

“The bold claims that manufacturers like to make about their PHEV cars are obviously way off the truth,” commented a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One independent energy economics specialist, who was not involved with the study, called the report a “very useful contribution” after a long period in which parts of the automotive sector argued there was too little data to accurately assess actual emissions.

“These findings demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of this evidence.”