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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating emissions than official figures indicate, according to a recent report.

Growing Gap In Lab and Actual Emissions

Data shows that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, according to research conducted by a advocacy organization. This differs sharply with laboratory estimates, which assumed a 75% decrease in pollution.

Analysts examined data from onboard energy use monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a lead analyst involved in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to total mileage. They found that only 27% of travel was done in electric mode, whereas official estimates suggested 84%.

Additionally, when running in electric mode, emission amounts were well above official estimates. That happened because electric motors were insufficiently powerful enough to function alone, resulting to engines using fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

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

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the mark,” commented a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from member states with significant automotive industries.

Some high-level politicians have suggested PHEVs as a potential “compromise” solution to include in the regulation.

One independent energy policy expert, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which segments of the car industry argued there was insufficient information to properly evaluate real-world emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” they said. “All policy adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”