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Plug-in hybrid cars emit nearly five times greater planet-heating emissions than official figures indicate, according to a new report.

Widening Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research carried out by a advocacy group. This differs significantly with lab estimates, which assumed a 75% decrease in emissions.

Analysts studied information from onboard fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery power compared to overall mileage. The team determined that just a quarter of driving was completed in EV mode, whereas lab estimates assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than official estimates. This occurred because EV motors were not strong enough to operate alone, resulting to combustion motors burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled several major automaker companies to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more per year in running costs than would be assumed under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” commented a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are little improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought back into political discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car sector and opposition from EU countries with significant automotive industries.

Some high-level officials have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

One external energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after years in which parts of the car industry claimed there was too little information to accurately assess real-world emissions.

“These findings show, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” they stated. “All regulatory changes concerning PHEVs should be made with utmost caution and in the light of that evidence.”