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Plug-in hybrid electric vehicles emit nearly 5x greater global warming emissions than official figures show, as per a recent report.

Growing Discrepancy Between Official and Actual Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a lead researcher involved in the study. “This discrepancy is growing and creates a serious problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric power relative to total mileage. They determined that just 27% of travel was done in electric mode, whereas official assumptions suggested 84%.

Even, when running in electric mode, pollution amounts were significantly higher than lab estimates. This occurred because EV motors were insufficiently powerful enough to function independently, resulting to engines burning fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several large automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 more annually in operating costs than is assumed under laboratory conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into political debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large car manufacturing.

Several high-level politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the research, called the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was too little information to accurately assess actual CO2 output.

“The results show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”