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PHEVs produce nearly five times greater global warming emissions than lab-reported figures indicate, according to a new report.

Growing Discrepancy Between Official and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles 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, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a senior analyst participating in the study. “This gap is widening and poses a serious issue. As a result, PHEVs pollute almost as much as petrol vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery power compared to overall mileage. They determined that just a quarter of driving was done in EV mode, whereas official assumptions suggested 84%.

Even, when running in electric mode, pollution levels were significantly higher than official projections. That happened because electric motors were not strong sufficient to function independently, leading to combustion motors using gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions allowed four large carmaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more per year in running expenses than would be estimated under laboratory tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into political discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant car industries.

Some senior politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which segments of the car sector argued there was too little information to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” the expert said. “All regulatory adjustments regarding PHEVs should be made with utmost care and considering that evidence.”