Plug-in Hybrid Vehicles Pollute Nearly as Heavily as Gasoline Vehicles, Study Finds

PHEVs produce nearly five times more global warming emissions than official figures indicate, according to a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” stated a senior analyst involved in the report. “This discrepancy is growing and creates a significant problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric power compared to overall distance. The team determined that just 27% of driving was completed in electric mode, whereas lab estimates assumed over four-fifths.

Even, when operating in electric mode, emission levels were significantly higher than official projections. This happened because EV motors were not strong enough to operate alone, leading to engines burning fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output enabled four large carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

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

“The strong claims that automakers like to make about their PHEV cars are clearly far from the mark,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large car manufacturing.

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

An independent energy economics expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive sector claimed there was too little data to accurately assess actual CO2 output.

“The results show, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional cars,” they said. “All policy changes regarding PHEVs should be implemented with extreme care and considering this evidence.”