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Plug-in hybrid electric vehicles emit nearly five times more global warming pollution than official figures show, according to a recent analysis.

Growing Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a advocacy group. That differs significantly with lab estimates, which suggested a 75% decrease in pollution.

Analysts examined data from onboard energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” said a lead analyst involved in the study. “This discrepancy is widening and creates a serious problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total distance. The team determined that just a quarter of travel was completed in EV mode, while official assumptions suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than official estimates. That happened because EV motors were not strong enough to function alone, leading to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Consequences

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

Furthermore, drivers of PHEVs would pay approximately €500 more annually in operating expenses than would be estimated under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV cars are clearly far from the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into political discussions as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant car manufacturing.

Some senior politicians have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

One external energy policy expert, who was not involved with the research, called the analysis a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was insufficient information to properly evaluate actual CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “Any policy adjustments regarding PHEVs should be made with extreme caution and considering this evidence.”