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Plug-in hybrid electric vehicles emit nearly 5x greater planet-heating pollution than lab-reported data indicate, as per a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit organization. This contrasts sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” stated a lead analyst participating in the study. “That discrepancy is widening and creates a significant problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to overall distance. They found that just 27% of driving was completed in EV mode, while official estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than official projections. That occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to engines using fossil fuels for almost one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed four major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 extra annually in running costs than is estimated under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have lately been drawn again into political debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” option to include in the legislation.

One external energy economics expert, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the automotive industry claimed there was too little data to properly evaluate actual CO2 output.

“These findings show, without question, that the gap between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they said. “Any regulatory adjustments concerning PHEVs should be made with extreme care and in the light of this data.”