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Plug-in hybrid cars emit nearly 5x greater planet-heating pollution than official data indicate, according to a new report.

Growing Discrepancy In Official and Real-World CO2 Output

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit organization. This contrasts significantly with lab estimates, which assumed a three-quarters reduction in pollution.

Analysts examined information from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead analyst participating in the study. “This discrepancy is widening and poses a serious problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in battery mode compared to overall mileage. The team found that just 27% of travel was completed in EV mode, while official assumptions assumed 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab estimates. This happened because EV motors were not strong enough to operate alone, resulting to engines using fossil fuels for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled four major carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in running costs than would be assumed under laboratory conditions.

“The strong claims that manufacturers 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 costs. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid vehicles have lately been brought back into political debates as automakers have pressed the European Union to relax CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with significant car manufacturing.

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

An independent energy economics expert, who was unaffiliated with the research, described the report a “very useful addition” after years in which parts of the automotive industry argued there was insufficient information to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of this data.”