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Plug-in hybrid cars emit almost 5x greater planet-heating pollution than official figures show, as per a new report.

Growing Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit group. That contrasts sharply with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts examined data from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” said a senior analyst participating in the report. “This gap is widening and poses a serious issue. Consequently, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to total distance. They found that just a quarter of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution amounts were significantly higher than official estimates. This happened because electric motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for nearly one-third of the travel covered in EV mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major carmaker groups to escape over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 extra annually in operating costs than would be assumed under laboratory tests.

“The strong statements that automakers often promote about their PHEV cars are clearly far from the mark,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been brought again into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large car manufacturing.

Several high-level officials have proposed PHEVs as a potential “flexibility” solution to include in the legislation.

One independent energy policy specialist, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little information to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert stated. “Any policy changes regarding PHEVs should be made with utmost caution and considering that evidence.”