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PHEVs emit nearly 5x greater global warming emissions than lab-reported figures indicate, according to a recent report.

Widening Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. That contrasts sharply with lab estimates, which assumed a 75% decrease in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” stated a lead researcher involved in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric power compared to total distance. The team found that only a quarter of driving was completed in electric mode, while official assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were significantly higher than official estimates. That happened because electric motors were not strong sufficient to function independently, leading to engines burning gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed four major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra per year in operating expenses than would be estimated under laboratory conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have recently been brought back into policy debates as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after years in which parts of the car industry argued there was too little data to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert said. “All policy adjustments regarding PHEVs should be implemented with utmost care and considering that evidence.”