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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating pollution than official data indicate, as per a new analysis.

Growing Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit group. That contrasts significantly with lab estimates, which suggested a 75% reduction in pollution.

Researchers studied data from in-vehicle energy use meters of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a senior analyst participating in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to total mileage. The team determined that only a quarter of travel was completed in EV mode, while lab assumptions assumed 84%.

Additionally, when running in EV mode, emission amounts were well above official projections. This happened because EV motors were not strong sufficient to operate independently, leading to combustion motors burning gasoline for almost one-third of the travel covered in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four major carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 extra per year in running costs than would be assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously far from the mark,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have recently been brought back into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large automotive manufacturing.

Some senior politicians have suggested PHEVs as a possible “compromise” option to include in the legislation.

One external energy policy expert, who was not involved with the study, described the report a “very useful contribution” after years in which parts of the car sector claimed there was too little data to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and considering this evidence.”