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Plug-in hybrid cars produce nearly 5x more planet-heating pollution than official figures indicate, as per a new analysis.

Widening Discrepancy In Official and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, according to research conducted by a advocacy group. This contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a senior analyst participating in the report. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall mileage. The team determined that just a quarter of driving was completed in electric mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, emission amounts were well above lab estimates. That occurred because electric motors were not strong sufficient to operate independently, leading to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV emissions allowed four major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend about €500 more annually in operating expenses than is assumed under laboratory tests.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the mark,” stated a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought back into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with significant automotive industries.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One external energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was insufficient information to accurately assess real-world CO2 output.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost caution and considering that evidence.”