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PHEVs release nearly five times more planet-heating pollution than official figures indicate, as per a new analysis.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, based on research carried out by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a lead researcher participating in the study. “This discrepancy is growing and poses a serious issue. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to overall mileage. They found that just 27% of travel was completed in electric mode, while official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, pollution amounts were significantly higher than official estimates. That occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines burning gasoline for nearly one-third of the travel covered in electric mode.

Regulatory and Economic Consequences

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

Additionally, owners of PHEVs could pay approximately €500 extra per year in operating expenses than is estimated under laboratory tests.

“The bold claims that automakers often promote about their PHEV cars are obviously far from the truth,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have lately been drawn again into policy debates as automakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from member states with large automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” solution to include in the legislation.

One independent energy economics expert, who was not involved with the research, described the report a “very useful addition” after a long period in which parts of the automotive industry argued there was insufficient information to properly assess real-world emissions.

“These findings 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 policy adjustments regarding PHEVs should be made with extreme caution and in the light of that data.”