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Plug-in hybrid cars release nearly 5x more global warming emissions than lab-reported data indicate, according to a new analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which suggested a 75% reduction in pollution.

Researchers studied information from onboard energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “That discrepancy is widening and poses a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to overall distance. They found that only a quarter of driving was done in electric mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to function independently, leading to combustion motors using fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV emissions allowed several major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more annually in operating expenses than is estimated under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been brought back into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One independent energy policy expert, who was not involved with the study, described the report a “highly valuable addition” after a long period in which segments of the automotive sector argued there was too little information to accurately assess actual CO2 output.

“The results show, without question, that the gap in official and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel cars,” they said. “All policy adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”