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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating pollution than official figures show, according to a recent report.

Growing Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit organization. That contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” stated a senior analyst involved in the study. “That gap is widening and poses a significant problem. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery power compared to overall mileage. The team 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 official projections. That happened because electric motors were insufficiently powerful enough to function alone, resulting to combustion motors burning gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four major automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in operating expenses than would be assumed under lab conditions.

“The strong claims that manufacturers often promote about their PHEV cars are obviously far from the mark,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Hybrid cars have recently been drawn back into political debates as automakers have lobbied the EU to weaken CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive industries.

Several high-level officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

One independent energy economics expert, who was not involved with the study, called the report a “highly valuable addition” after years in which segments of the automotive sector argued there was insufficient data to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and considering this data.”