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Plug-in hybrid electric vehicles produce almost 5x more planet-heating pollution than lab-reported data indicate, as per a recent analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel vehicles, based on research carried out by a non-profit organization. That contrasts sharply with laboratory tests, which assumed a 75% decrease in pollution.

Analysts studied information from onboard energy use meters of 800,000 cars sold in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a senior analyst participating in the study. “That discrepancy is widening and creates a serious issue. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric mode compared to total mileage. They found that just 27% of driving was completed in EV mode, while lab estimates suggested 84%.

Additionally, when operating in electric mode, emission levels were well above official estimates. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors using gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions enabled four large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in running costs than is assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV vehicles are clearly far from the truth,” stated a automotive analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large automotive manufacturing.

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

One independent energy policy specialist, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was too little data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert stated. “All policy adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”