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PHEVs emit nearly five times more global warming pollution than lab-reported figures indicate, according to a recent report.

Widening Gap In Official and Real-World CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy organization. That differs significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a senior researcher involved in the study. “That gap is growing and poses a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Behind the Discrepancy

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to total mileage. The team determined that only a quarter of travel was completed in electric mode, while official assumptions suggested over four-fifths.

Additionally, when running in electric mode, pollution levels were significantly higher than lab projections. That occurred because EV motors were not strong sufficient to function independently, resulting to engines using gasoline for almost one-third of the distance covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed four major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in running costs than is assumed under laboratory conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into political discussions as automakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and opposition from member states with significant car industries.

Some high-level politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the legislation.

One independent energy economics specialist, who was not involved with the study, called the report a “highly valuable contribution” after a long period in which parts of the car sector claimed there was too little data to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional vehicles,” they said. “All regulatory changes concerning PHEVs should be made with utmost caution and considering this data.”