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Plug-in hybrid electric vehicles emit nearly 5x greater planet-heating pollution than official figures show, as per a recent report.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy organization. That differs sharply with lab tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a lead researcher involved in the study. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric power relative to overall mileage. The team determined that only 27% of travel was done in electric mode, whereas official assumptions suggested 84%.

Even, when operating in electric mode, pollution amounts were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors burning fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several major carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 more per year in operating expenses than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the mark,” commented a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with significant automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after years in which parts of the automotive industry argued there was too little data to accurately assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel cars,” they stated. “Any policy adjustments regarding PHEVs should be made with utmost care and considering that data.”