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Plug-in hybrid electric vehicles release almost five times more global warming emissions than official figures show, as per a new analysis.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit organization. This contrasts sharply with lab tests, which assumed a three-quarters reduction in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a lead analyst participating in the report. “That gap is growing and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to total mileage. They determined that just 27% of travel was done in EV mode, whereas lab assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were well above official projections. That occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 more per year in operating costs than is estimated under laboratory conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been brought again into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large car manufacturing.

Some high-level politicians have proposed PHEVs as a possible “flexibility” option to include in the legislation.

An independent energy policy specialist, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was too little data to properly assess actual emissions.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they stated. “All policy adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”