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PHEVs release nearly 5x greater global warming pollution than lab-reported figures show, according to a new analysis.

Widening Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy group. That contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers studied information from onboard fuel consumption monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” stated a senior researcher involved in the study. “That gap is widening and creates a significant issue. As a result, PHEVs emit almost as much as petrol cars.”

Key Reasons Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric power relative to total mileage. They found that only a quarter of driving was done in EV mode, while lab estimates assumed over four-fifths.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab projections. This happened because electric motors were not strong sufficient to operate alone, leading to combustion motors burning fossil fuels for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output allowed four major carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more per year in operating costs than is estimated under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been drawn again into policy debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant automotive industries.

Several senior politicians have suggested PHEVs as a possible “compromise” option to include in the legislation.

An independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be implemented with utmost care and in the light of this data.”