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PHEVs emit nearly 5x greater planet-heating emissions than lab-reported figures indicate, according to a new report.

Widening Discrepancy In Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That contrasts significantly with lab tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from onboard fuel consumption meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a senior researcher participating in the study. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric mode relative to total mileage. They found that just a quarter of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab estimates. That happened because EV motors were not strong enough to function independently, resulting to combustion motors using gasoline for nearly one-third of the travel covered in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output enabled several major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in operating expenses than would be estimated under lab conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have lately been brought again into policy discussions as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant automotive manufacturing.

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

An independent energy policy expert, who was unaffiliated with the study, described the report a “highly valuable contribution” after years in which segments of the car sector argued there was too little information to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that data.”